1 /*
2 * Copyright (c) 2000, 2010, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
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23 */
24
25 #include "precompiled.hpp"
26 #include "compiler/compileLog.hpp"
27 #include "memory/allocation.inline.hpp"
28 #include "opto/addnode.hpp"
29 #include "opto/callnode.hpp"
30 #include "opto/connode.hpp"
31 #include "opto/divnode.hpp"
32 #include "opto/loopnode.hpp"
33 #include "opto/mulnode.hpp"
34 #include "opto/rootnode.hpp"
35 #include "opto/runtime.hpp"
36 #include "opto/subnode.hpp"
37
38 //------------------------------is_loop_exit-----------------------------------
39 // Given an IfNode, return the loop-exiting projection or NULL if both
40 // arms remain in the loop.
41 Node *IdealLoopTree::is_loop_exit(Node *iff) const {
42 if( iff->outcnt() != 2 ) return NULL; // Ignore partially dead tests
43 PhaseIdealLoop *phase = _phase;
44 // Test is an IfNode, has 2 projections. If BOTH are in the loop
45 // we need loop unswitching instead of peeling.
46 if( !is_member(phase->get_loop( iff->raw_out(0) )) )
47 return iff->raw_out(0);
48 if( !is_member(phase->get_loop( iff->raw_out(1) )) )
49 return iff->raw_out(1);
50 return NULL;
51 }
52
53
54 //=============================================================================
55
56
57 //------------------------------record_for_igvn----------------------------
58 // Put loop body on igvn work list
59 void IdealLoopTree::record_for_igvn() {
60 for( uint i = 0; i < _body.size(); i++ ) {
61 Node *n = _body.at(i);
62 _phase->_igvn._worklist.push(n);
63 }
64 }
65
66 //------------------------------compute_profile_trip_cnt----------------------------
67 // Compute loop trip count from profile data as
68 // (backedge_count + loop_exit_count) / loop_exit_count
69 void IdealLoopTree::compute_profile_trip_cnt( PhaseIdealLoop *phase ) {
70 if (!_head->is_CountedLoop()) {
71 return;
72 }
73 CountedLoopNode* head = _head->as_CountedLoop();
74 if (head->profile_trip_cnt() != COUNT_UNKNOWN) {
75 return; // Already computed
76 }
77 float trip_cnt = (float)max_jint; // default is big
78
79 Node* back = head->in(LoopNode::LoopBackControl);
80 while (back != head) {
81 if ((back->Opcode() == Op_IfTrue || back->Opcode() == Op_IfFalse) &&
82 back->in(0) &&
83 back->in(0)->is_If() &&
84 back->in(0)->as_If()->_fcnt != COUNT_UNKNOWN &&
85 back->in(0)->as_If()->_prob != PROB_UNKNOWN) {
86 break;
87 }
88 back = phase->idom(back);
89 }
90 if (back != head) {
91 assert((back->Opcode() == Op_IfTrue || back->Opcode() == Op_IfFalse) &&
92 back->in(0), "if-projection exists");
93 IfNode* back_if = back->in(0)->as_If();
94 float loop_back_cnt = back_if->_fcnt * back_if->_prob;
95
96 // Now compute a loop exit count
97 float loop_exit_cnt = 0.0f;
98 for( uint i = 0; i < _body.size(); i++ ) {
99 Node *n = _body[i];
100 if( n->is_If() ) {
101 IfNode *iff = n->as_If();
102 if( iff->_fcnt != COUNT_UNKNOWN && iff->_prob != PROB_UNKNOWN ) {
103 Node *exit = is_loop_exit(iff);
104 if( exit ) {
105 float exit_prob = iff->_prob;
106 if (exit->Opcode() == Op_IfFalse) exit_prob = 1.0 - exit_prob;
107 if (exit_prob > PROB_MIN) {
108 float exit_cnt = iff->_fcnt * exit_prob;
109 loop_exit_cnt += exit_cnt;
110 }
111 }
112 }
113 }
114 }
115 if (loop_exit_cnt > 0.0f) {
116 trip_cnt = (loop_back_cnt + loop_exit_cnt) / loop_exit_cnt;
117 } else {
118 // No exit count so use
119 trip_cnt = loop_back_cnt;
120 }
121 }
122 #ifndef PRODUCT
123 if (TraceProfileTripCount) {
124 tty->print_cr("compute_profile_trip_cnt lp: %d cnt: %f\n", head->_idx, trip_cnt);
125 }
126 #endif
127 head->set_profile_trip_cnt(trip_cnt);
128 }
129
130 //---------------------is_invariant_addition-----------------------------
131 // Return nonzero index of invariant operand for an Add or Sub
132 // of (nonconstant) invariant and variant values. Helper for reassociate_invariants.
133 int IdealLoopTree::is_invariant_addition(Node* n, PhaseIdealLoop *phase) {
134 int op = n->Opcode();
135 if (op == Op_AddI || op == Op_SubI) {
136 bool in1_invar = this->is_invariant(n->in(1));
137 bool in2_invar = this->is_invariant(n->in(2));
138 if (in1_invar && !in2_invar) return 1;
139 if (!in1_invar && in2_invar) return 2;
140 }
141 return 0;
142 }
143
144 //---------------------reassociate_add_sub-----------------------------
145 // Reassociate invariant add and subtract expressions:
146 //
147 // inv1 + (x + inv2) => ( inv1 + inv2) + x
148 // (x + inv2) + inv1 => ( inv1 + inv2) + x
149 // inv1 + (x - inv2) => ( inv1 - inv2) + x
150 // inv1 - (inv2 - x) => ( inv1 - inv2) + x
151 // (x + inv2) - inv1 => (-inv1 + inv2) + x
152 // (x - inv2) + inv1 => ( inv1 - inv2) + x
153 // (x - inv2) - inv1 => (-inv1 - inv2) + x
154 // inv1 + (inv2 - x) => ( inv1 + inv2) - x
155 // inv1 - (x - inv2) => ( inv1 + inv2) - x
156 // (inv2 - x) + inv1 => ( inv1 + inv2) - x
157 // (inv2 - x) - inv1 => (-inv1 + inv2) - x
158 // inv1 - (x + inv2) => ( inv1 - inv2) - x
159 //
160 Node* IdealLoopTree::reassociate_add_sub(Node* n1, PhaseIdealLoop *phase) {
161 if (!n1->is_Add() && !n1->is_Sub() || n1->outcnt() == 0) return NULL;
162 if (is_invariant(n1)) return NULL;
163 int inv1_idx = is_invariant_addition(n1, phase);
164 if (!inv1_idx) return NULL;
165 // Don't mess with add of constant (igvn moves them to expression tree root.)
166 if (n1->is_Add() && n1->in(2)->is_Con()) return NULL;
167 Node* inv1 = n1->in(inv1_idx);
168 Node* n2 = n1->in(3 - inv1_idx);
169 int inv2_idx = is_invariant_addition(n2, phase);
170 if (!inv2_idx) return NULL;
171 Node* x = n2->in(3 - inv2_idx);
172 Node* inv2 = n2->in(inv2_idx);
173
174 bool neg_x = n2->is_Sub() && inv2_idx == 1;
175 bool neg_inv2 = n2->is_Sub() && inv2_idx == 2;
176 bool neg_inv1 = n1->is_Sub() && inv1_idx == 2;
177 if (n1->is_Sub() && inv1_idx == 1) {
178 neg_x = !neg_x;
179 neg_inv2 = !neg_inv2;
180 }
181 Node* inv1_c = phase->get_ctrl(inv1);
182 Node* inv2_c = phase->get_ctrl(inv2);
183 Node* n_inv1;
184 if (neg_inv1) {
185 Node *zero = phase->_igvn.intcon(0);
186 phase->set_ctrl(zero, phase->C->root());
187 n_inv1 = new (phase->C, 3) SubINode(zero, inv1);
188 phase->register_new_node(n_inv1, inv1_c);
189 } else {
190 n_inv1 = inv1;
191 }
192 Node* inv;
193 if (neg_inv2) {
194 inv = new (phase->C, 3) SubINode(n_inv1, inv2);
195 } else {
196 inv = new (phase->C, 3) AddINode(n_inv1, inv2);
197 }
198 phase->register_new_node(inv, phase->get_early_ctrl(inv));
199
200 Node* addx;
201 if (neg_x) {
202 addx = new (phase->C, 3) SubINode(inv, x);
203 } else {
204 addx = new (phase->C, 3) AddINode(x, inv);
205 }
206 phase->register_new_node(addx, phase->get_ctrl(x));
207 phase->_igvn.replace_node(n1, addx);
208 return addx;
209 }
210
211 //---------------------reassociate_invariants-----------------------------
212 // Reassociate invariant expressions:
213 void IdealLoopTree::reassociate_invariants(PhaseIdealLoop *phase) {
214 for (int i = _body.size() - 1; i >= 0; i--) {
215 Node *n = _body.at(i);
216 for (int j = 0; j < 5; j++) {
217 Node* nn = reassociate_add_sub(n, phase);
218 if (nn == NULL) break;
219 n = nn; // again
220 };
221 }
222 }
223
224 //------------------------------policy_peeling---------------------------------
225 // Return TRUE or FALSE if the loop should be peeled or not. Peel if we can
226 // make some loop-invariant test (usually a null-check) happen before the loop.
227 bool IdealLoopTree::policy_peeling( PhaseIdealLoop *phase ) const {
228 Node *test = ((IdealLoopTree*)this)->tail();
229 int body_size = ((IdealLoopTree*)this)->_body.size();
230 int uniq = phase->C->unique();
231 // Peeling does loop cloning which can result in O(N^2) node construction
232 if( body_size > 255 /* Prevent overflow for large body_size */
233 || (body_size * body_size + uniq > MaxNodeLimit) ) {
234 return false; // too large to safely clone
235 }
236 while( test != _head ) { // Scan till run off top of loop
237 if( test->is_If() ) { // Test?
238 Node *ctrl = phase->get_ctrl(test->in(1));
239 if (ctrl->is_top())
240 return false; // Found dead test on live IF? No peeling!
241 // Standard IF only has one input value to check for loop invariance
242 assert( test->Opcode() == Op_If || test->Opcode() == Op_CountedLoopEnd, "Check this code when new subtype is added");
243 // Condition is not a member of this loop?
244 if( !is_member(phase->get_loop(ctrl)) &&
245 is_loop_exit(test) )
246 return true; // Found reason to peel!
247 }
248 // Walk up dominators to loop _head looking for test which is
249 // executed on every path thru loop.
250 test = phase->idom(test);
251 }
252 return false;
253 }
254
255 //------------------------------peeled_dom_test_elim---------------------------
256 // If we got the effect of peeling, either by actually peeling or by making
257 // a pre-loop which must execute at least once, we can remove all
258 // loop-invariant dominated tests in the main body.
259 void PhaseIdealLoop::peeled_dom_test_elim( IdealLoopTree *loop, Node_List &old_new ) {
260 bool progress = true;
261 while( progress ) {
262 progress = false; // Reset for next iteration
263 Node *prev = loop->_head->in(LoopNode::LoopBackControl);//loop->tail();
264 Node *test = prev->in(0);
265 while( test != loop->_head ) { // Scan till run off top of loop
266
267 int p_op = prev->Opcode();
268 if( (p_op == Op_IfFalse || p_op == Op_IfTrue) &&
269 test->is_If() && // Test?
270 !test->in(1)->is_Con() && // And not already obvious?
271 // Condition is not a member of this loop?
272 !loop->is_member(get_loop(get_ctrl(test->in(1))))){
273 // Walk loop body looking for instances of this test
274 for( uint i = 0; i < loop->_body.size(); i++ ) {
275 Node *n = loop->_body.at(i);
276 if( n->is_If() && n->in(1) == test->in(1) /*&& n != loop->tail()->in(0)*/ ) {
277 // IfNode was dominated by version in peeled loop body
278 progress = true;
279 dominated_by( old_new[prev->_idx], n );
280 }
281 }
282 }
283 prev = test;
284 test = idom(test);
285 } // End of scan tests in loop
286
287 } // End of while( progress )
288 }
289
290 //------------------------------do_peeling-------------------------------------
291 // Peel the first iteration of the given loop.
292 // Step 1: Clone the loop body. The clone becomes the peeled iteration.
293 // The pre-loop illegally has 2 control users (old & new loops).
294 // Step 2: Make the old-loop fall-in edges point to the peeled iteration.
295 // Do this by making the old-loop fall-in edges act as if they came
296 // around the loopback from the prior iteration (follow the old-loop
297 // backedges) and then map to the new peeled iteration. This leaves
298 // the pre-loop with only 1 user (the new peeled iteration), but the
299 // peeled-loop backedge has 2 users.
300 // Step 3: Cut the backedge on the clone (so its not a loop) and remove the
301 // extra backedge user.
302 void PhaseIdealLoop::do_peeling( IdealLoopTree *loop, Node_List &old_new ) {
303
304 C->set_major_progress();
305 // Peeling a 'main' loop in a pre/main/post situation obfuscates the
306 // 'pre' loop from the main and the 'pre' can no longer have it's
307 // iterations adjusted. Therefore, we need to declare this loop as
308 // no longer a 'main' loop; it will need new pre and post loops before
309 // we can do further RCE.
310 Node *h = loop->_head;
311 if( h->is_CountedLoop() ) {
312 CountedLoopNode *cl = h->as_CountedLoop();
313 assert(cl->trip_count() > 0, "peeling a fully unrolled loop");
314 cl->set_trip_count(cl->trip_count() - 1);
315 if( cl->is_main_loop() ) {
316 cl->set_normal_loop();
317 #ifndef PRODUCT
318 if( PrintOpto && VerifyLoopOptimizations ) {
319 tty->print("Peeling a 'main' loop; resetting to 'normal' ");
320 loop->dump_head();
321 }
322 #endif
323 }
324 }
325
326 // Step 1: Clone the loop body. The clone becomes the peeled iteration.
327 // The pre-loop illegally has 2 control users (old & new loops).
328 clone_loop( loop, old_new, dom_depth(loop->_head) );
329
330
331 // Step 2: Make the old-loop fall-in edges point to the peeled iteration.
332 // Do this by making the old-loop fall-in edges act as if they came
333 // around the loopback from the prior iteration (follow the old-loop
334 // backedges) and then map to the new peeled iteration. This leaves
335 // the pre-loop with only 1 user (the new peeled iteration), but the
336 // peeled-loop backedge has 2 users.
337 for (DUIterator_Fast jmax, j = loop->_head->fast_outs(jmax); j < jmax; j++) {
338 Node* old = loop->_head->fast_out(j);
339 if( old->in(0) == loop->_head && old->req() == 3 &&
340 (old->is_Loop() || old->is_Phi()) ) {
341 Node *new_exit_value = old_new[old->in(LoopNode::LoopBackControl)->_idx];
342 if( !new_exit_value ) // Backedge value is ALSO loop invariant?
343 // Then loop body backedge value remains the same.
344 new_exit_value = old->in(LoopNode::LoopBackControl);
345 _igvn.hash_delete(old);
346 old->set_req(LoopNode::EntryControl, new_exit_value);
347 }
348 }
349
350
351 // Step 3: Cut the backedge on the clone (so its not a loop) and remove the
352 // extra backedge user.
353 Node *nnn = old_new[loop->_head->_idx];
354 _igvn.hash_delete(nnn);
355 nnn->set_req(LoopNode::LoopBackControl, C->top());
356 for (DUIterator_Fast j2max, j2 = nnn->fast_outs(j2max); j2 < j2max; j2++) {
357 Node* use = nnn->fast_out(j2);
358 if( use->in(0) == nnn && use->req() == 3 && use->is_Phi() ) {
359 _igvn.hash_delete(use);
360 use->set_req(LoopNode::LoopBackControl, C->top());
361 }
362 }
363
364
365 // Step 4: Correct dom-depth info. Set to loop-head depth.
366 int dd = dom_depth(loop->_head);
367 set_idom(loop->_head, loop->_head->in(1), dd);
368 for (uint j3 = 0; j3 < loop->_body.size(); j3++) {
369 Node *old = loop->_body.at(j3);
370 Node *nnn = old_new[old->_idx];
371 if (!has_ctrl(nnn))
372 set_idom(nnn, idom(nnn), dd-1);
373 // While we're at it, remove any SafePoints from the peeled code
374 if( old->Opcode() == Op_SafePoint ) {
375 Node *nnn = old_new[old->_idx];
376 lazy_replace(nnn,nnn->in(TypeFunc::Control));
377 }
378 }
379
380 // Now force out all loop-invariant dominating tests. The optimizer
381 // finds some, but we _know_ they are all useless.
382 peeled_dom_test_elim(loop,old_new);
383
384 loop->record_for_igvn();
385 }
386
387 //------------------------------policy_maximally_unroll------------------------
388 // Return exact loop trip count, or 0 if not maximally unrolling
389 bool IdealLoopTree::policy_maximally_unroll( PhaseIdealLoop *phase ) const {
390 CountedLoopNode *cl = _head->as_CountedLoop();
391 assert( cl->is_normal_loop(), "" );
392
393 Node *init_n = cl->init_trip();
394 Node *limit_n = cl->limit();
395
396 // Non-constant bounds
397 if( init_n == NULL || !init_n->is_Con() ||
398 limit_n == NULL || !limit_n->is_Con() ||
399 // protect against stride not being a constant
400 !cl->stride_is_con() ) {
401 return false;
402 }
403 int init = init_n->get_int();
404 int limit = limit_n->get_int();
405 int span = limit - init;
406 int stride = cl->stride_con();
407
408 if (init >= limit || stride > span) {
409 // return a false (no maximally unroll) and the regular unroll/peel
410 // route will make a small mess which CCP will fold away.
411 return false;
412 }
413 uint trip_count = span/stride; // trip_count can be greater than 2 Gig.
414 assert( (int)trip_count*stride == span, "must divide evenly" );
415
416 // Real policy: if we maximally unroll, does it get too big?
417 // Allow the unrolled mess to get larger than standard loop
418 // size. After all, it will no longer be a loop.
419 uint body_size = _body.size();
420 uint unroll_limit = (uint)LoopUnrollLimit * 4;
421 assert( (intx)unroll_limit == LoopUnrollLimit * 4, "LoopUnrollLimit must fit in 32bits");
422 cl->set_trip_count(trip_count);
423 if( trip_count <= unroll_limit && body_size <= unroll_limit ) {
424 uint new_body_size = body_size * trip_count;
425 if (new_body_size <= unroll_limit &&
426 body_size == new_body_size / trip_count &&
427 // Unrolling can result in a large amount of node construction
428 new_body_size < MaxNodeLimit - phase->C->unique()) {
429 return true; // maximally unroll
430 }
431 }
432
433 return false; // Do not maximally unroll
434 }
435
436
437 //------------------------------policy_unroll----------------------------------
438 // Return TRUE or FALSE if the loop should be unrolled or not. Unroll if
439 // the loop is a CountedLoop and the body is small enough.
440 bool IdealLoopTree::policy_unroll( PhaseIdealLoop *phase ) const {
441
442 CountedLoopNode *cl = _head->as_CountedLoop();
443 assert( cl->is_normal_loop() || cl->is_main_loop(), "" );
444
445 // protect against stride not being a constant
446 if( !cl->stride_is_con() ) return false;
447
448 // protect against over-unrolling
449 if( cl->trip_count() <= 1 ) return false;
450
451 int future_unroll_ct = cl->unrolled_count() * 2;
452
453 // Don't unroll if the next round of unrolling would push us
454 // over the expected trip count of the loop. One is subtracted
455 // from the expected trip count because the pre-loop normally
456 // executes 1 iteration.
457 if (UnrollLimitForProfileCheck > 0 &&
458 cl->profile_trip_cnt() != COUNT_UNKNOWN &&
459 future_unroll_ct > UnrollLimitForProfileCheck &&
460 (float)future_unroll_ct > cl->profile_trip_cnt() - 1.0) {
461 return false;
462 }
463
464 // When unroll count is greater than LoopUnrollMin, don't unroll if:
465 // the residual iterations are more than 10% of the trip count
466 // and rounds of "unroll,optimize" are not making significant progress
467 // Progress defined as current size less than 20% larger than previous size.
468 if (UseSuperWord && cl->node_count_before_unroll() > 0 &&
469 future_unroll_ct > LoopUnrollMin &&
470 (future_unroll_ct - 1) * 10.0 > cl->profile_trip_cnt() &&
471 1.2 * cl->node_count_before_unroll() < (double)_body.size()) {
472 return false;
473 }
474
475 Node *init_n = cl->init_trip();
476 Node *limit_n = cl->limit();
477 // Non-constant bounds.
478 // Protect against over-unrolling when init or/and limit are not constant
479 // (so that trip_count's init value is maxint) but iv range is known.
480 if( init_n == NULL || !init_n->is_Con() ||
481 limit_n == NULL || !limit_n->is_Con() ) {
482 Node* phi = cl->phi();
483 if( phi != NULL ) {
484 assert(phi->is_Phi() && phi->in(0) == _head, "Counted loop should have iv phi.");
485 const TypeInt* iv_type = phase->_igvn.type(phi)->is_int();
486 int next_stride = cl->stride_con() * 2; // stride after this unroll
487 if( next_stride > 0 ) {
488 if( iv_type->_lo + next_stride <= iv_type->_lo || // overflow
489 iv_type->_lo + next_stride > iv_type->_hi ) {
490 return false; // over-unrolling
491 }
492 } else if( next_stride < 0 ) {
493 if( iv_type->_hi + next_stride >= iv_type->_hi || // overflow
494 iv_type->_hi + next_stride < iv_type->_lo ) {
495 return false; // over-unrolling
496 }
497 }
498 }
499 }
500
501 // Adjust body_size to determine if we unroll or not
502 uint body_size = _body.size();
503 // Key test to unroll CaffeineMark's Logic test
504 int xors_in_loop = 0;
505 // Also count ModL, DivL and MulL which expand mightly
506 for( uint k = 0; k < _body.size(); k++ ) {
507 switch( _body.at(k)->Opcode() ) {
508 case Op_XorI: xors_in_loop++; break; // CaffeineMark's Logic test
509 case Op_ModL: body_size += 30; break;
510 case Op_DivL: body_size += 30; break;
511 case Op_MulL: body_size += 10; break;
512 }
513 }
514
515 // Check for being too big
516 if( body_size > (uint)LoopUnrollLimit ) {
517 if( xors_in_loop >= 4 && body_size < (uint)LoopUnrollLimit*4) return true;
518 // Normal case: loop too big
519 return false;
520 }
521
522 // Check for stride being a small enough constant
523 if( abs(cl->stride_con()) > (1<<3) ) return false;
524
525 // Unroll once! (Each trip will soon do double iterations)
526 return true;
527 }
528
529 //------------------------------policy_align-----------------------------------
530 // Return TRUE or FALSE if the loop should be cache-line aligned. Gather the
531 // expression that does the alignment. Note that only one array base can be
532 // aligned in a loop (unless the VM guarantees mutual alignment). Note that
533 // if we vectorize short memory ops into longer memory ops, we may want to
534 // increase alignment.
535 bool IdealLoopTree::policy_align( PhaseIdealLoop *phase ) const {
536 return false;
537 }
538
539 //------------------------------policy_range_check-----------------------------
540 // Return TRUE or FALSE if the loop should be range-check-eliminated.
541 // Actually we do iteration-splitting, a more powerful form of RCE.
542 bool IdealLoopTree::policy_range_check( PhaseIdealLoop *phase ) const {
543 if( !RangeCheckElimination ) return false;
544
545 CountedLoopNode *cl = _head->as_CountedLoop();
546 // If we unrolled with no intention of doing RCE and we later
547 // changed our minds, we got no pre-loop. Either we need to
548 // make a new pre-loop, or we gotta disallow RCE.
549 if( cl->is_main_no_pre_loop() ) return false; // Disallowed for now.
550 Node *trip_counter = cl->phi();
551
552 // Check loop body for tests of trip-counter plus loop-invariant vs
553 // loop-invariant.
554 for( uint i = 0; i < _body.size(); i++ ) {
555 Node *iff = _body[i];
556 if( iff->Opcode() == Op_If ) { // Test?
557
558 // Comparing trip+off vs limit
559 Node *bol = iff->in(1);
560 if( bol->req() != 2 ) continue; // dead constant test
561 if (!bol->is_Bool()) {
562 assert(UseLoopPredicate && bol->Opcode() == Op_Conv2B, "predicate check only");
563 continue;
564 }
565 Node *cmp = bol->in(1);
566
567 Node *rc_exp = cmp->in(1);
568 Node *limit = cmp->in(2);
569
570 Node *limit_c = phase->get_ctrl(limit);
571 if( limit_c == phase->C->top() )
572 return false; // Found dead test on live IF? No RCE!
573 if( is_member(phase->get_loop(limit_c) ) ) {
574 // Compare might have operands swapped; commute them
575 rc_exp = cmp->in(2);
576 limit = cmp->in(1);
577 limit_c = phase->get_ctrl(limit);
578 if( is_member(phase->get_loop(limit_c) ) )
579 continue; // Both inputs are loop varying; cannot RCE
580 }
581
582 if (!phase->is_scaled_iv_plus_offset(rc_exp, trip_counter, NULL, NULL)) {
583 continue;
584 }
585 // Yeah! Found a test like 'trip+off vs limit'
586 // Test is an IfNode, has 2 projections. If BOTH are in the loop
587 // we need loop unswitching instead of iteration splitting.
588 if( is_loop_exit(iff) )
589 return true; // Found reason to split iterations
590 } // End of is IF
591 }
592
593 return false;
594 }
595
596 //------------------------------policy_peel_only-------------------------------
597 // Return TRUE or FALSE if the loop should NEVER be RCE'd or aligned. Useful
598 // for unrolling loops with NO array accesses.
599 bool IdealLoopTree::policy_peel_only( PhaseIdealLoop *phase ) const {
600
601 for( uint i = 0; i < _body.size(); i++ )
602 if( _body[i]->is_Mem() )
603 return false;
604
605 // No memory accesses at all!
606 return true;
607 }
608
609 //------------------------------clone_up_backedge_goo--------------------------
610 // If Node n lives in the back_ctrl block and cannot float, we clone a private
611 // version of n in preheader_ctrl block and return that, otherwise return n.
612 Node *PhaseIdealLoop::clone_up_backedge_goo( Node *back_ctrl, Node *preheader_ctrl, Node *n ) {
613 if( get_ctrl(n) != back_ctrl ) return n;
614
615 Node *x = NULL; // If required, a clone of 'n'
616 // Check for 'n' being pinned in the backedge.
617 if( n->in(0) && n->in(0) == back_ctrl ) {
618 x = n->clone(); // Clone a copy of 'n' to preheader
619 x->set_req( 0, preheader_ctrl ); // Fix x's control input to preheader
620 }
621
622 // Recursive fixup any other input edges into x.
623 // If there are no changes we can just return 'n', otherwise
624 // we need to clone a private copy and change it.
625 for( uint i = 1; i < n->req(); i++ ) {
626 Node *g = clone_up_backedge_goo( back_ctrl, preheader_ctrl, n->in(i) );
627 if( g != n->in(i) ) {
628 if( !x )
629 x = n->clone();
630 x->set_req(i, g);
631 }
632 }
633 if( x ) { // x can legally float to pre-header location
634 register_new_node( x, preheader_ctrl );
635 return x;
636 } else { // raise n to cover LCA of uses
637 set_ctrl( n, find_non_split_ctrl(back_ctrl->in(0)) );
638 }
639 return n;
640 }
641
642 //------------------------------insert_pre_post_loops--------------------------
643 // Insert pre and post loops. If peel_only is set, the pre-loop can not have
644 // more iterations added. It acts as a 'peel' only, no lower-bound RCE, no
645 // alignment. Useful to unroll loops that do no array accesses.
646 void PhaseIdealLoop::insert_pre_post_loops( IdealLoopTree *loop, Node_List &old_new, bool peel_only ) {
647
648 C->set_major_progress();
649
650 // Find common pieces of the loop being guarded with pre & post loops
651 CountedLoopNode *main_head = loop->_head->as_CountedLoop();
652 assert( main_head->is_normal_loop(), "" );
653 CountedLoopEndNode *main_end = main_head->loopexit();
654 assert( main_end->outcnt() == 2, "1 true, 1 false path only" );
655 uint dd_main_head = dom_depth(main_head);
656 uint max = main_head->outcnt();
657
658 Node *pre_header= main_head->in(LoopNode::EntryControl);
659 Node *init = main_head->init_trip();
660 Node *incr = main_end ->incr();
661 Node *limit = main_end ->limit();
662 Node *stride = main_end ->stride();
663 Node *cmp = main_end ->cmp_node();
664 BoolTest::mask b_test = main_end->test_trip();
665
666 // Need only 1 user of 'bol' because I will be hacking the loop bounds.
667 Node *bol = main_end->in(CountedLoopEndNode::TestValue);
668 if( bol->outcnt() != 1 ) {
669 bol = bol->clone();
670 register_new_node(bol,main_end->in(CountedLoopEndNode::TestControl));
671 _igvn.hash_delete(main_end);
672 main_end->set_req(CountedLoopEndNode::TestValue, bol);
673 }
674 // Need only 1 user of 'cmp' because I will be hacking the loop bounds.
675 if( cmp->outcnt() != 1 ) {
676 cmp = cmp->clone();
677 register_new_node(cmp,main_end->in(CountedLoopEndNode::TestControl));
678 _igvn.hash_delete(bol);
679 bol->set_req(1, cmp);
680 }
681
682 //------------------------------
683 // Step A: Create Post-Loop.
684 Node* main_exit = main_end->proj_out(false);
685 assert( main_exit->Opcode() == Op_IfFalse, "" );
686 int dd_main_exit = dom_depth(main_exit);
687
688 // Step A1: Clone the loop body. The clone becomes the post-loop. The main
689 // loop pre-header illegally has 2 control users (old & new loops).
690 clone_loop( loop, old_new, dd_main_exit );
691 assert( old_new[main_end ->_idx]->Opcode() == Op_CountedLoopEnd, "" );
692 CountedLoopNode *post_head = old_new[main_head->_idx]->as_CountedLoop();
693 post_head->set_post_loop(main_head);
694
695 // Reduce the post-loop trip count.
696 CountedLoopEndNode* post_end = old_new[main_end ->_idx]->as_CountedLoopEnd();
697 post_end->_prob = PROB_FAIR;
698
699 // Build the main-loop normal exit.
700 IfFalseNode *new_main_exit = new (C, 1) IfFalseNode(main_end);
701 _igvn.register_new_node_with_optimizer( new_main_exit );
702 set_idom(new_main_exit, main_end, dd_main_exit );
703 set_loop(new_main_exit, loop->_parent);
704
705 // Step A2: Build a zero-trip guard for the post-loop. After leaving the
706 // main-loop, the post-loop may not execute at all. We 'opaque' the incr
707 // (the main-loop trip-counter exit value) because we will be changing
708 // the exit value (via unrolling) so we cannot constant-fold away the zero
709 // trip guard until all unrolling is done.
710 Node *zer_opaq = new (C, 2) Opaque1Node(C, incr);
711 Node *zer_cmp = new (C, 3) CmpINode( zer_opaq, limit );
712 Node *zer_bol = new (C, 2) BoolNode( zer_cmp, b_test );
713 register_new_node( zer_opaq, new_main_exit );
714 register_new_node( zer_cmp , new_main_exit );
715 register_new_node( zer_bol , new_main_exit );
716
717 // Build the IfNode
718 IfNode *zer_iff = new (C, 2) IfNode( new_main_exit, zer_bol, PROB_FAIR, COUNT_UNKNOWN );
719 _igvn.register_new_node_with_optimizer( zer_iff );
720 set_idom(zer_iff, new_main_exit, dd_main_exit);
721 set_loop(zer_iff, loop->_parent);
722
723 // Plug in the false-path, taken if we need to skip post-loop
724 _igvn.hash_delete( main_exit );
725 main_exit->set_req(0, zer_iff);
726 _igvn._worklist.push(main_exit);
727 set_idom(main_exit, zer_iff, dd_main_exit);
728 set_idom(main_exit->unique_out(), zer_iff, dd_main_exit);
729 // Make the true-path, must enter the post loop
730 Node *zer_taken = new (C, 1) IfTrueNode( zer_iff );
731 _igvn.register_new_node_with_optimizer( zer_taken );
732 set_idom(zer_taken, zer_iff, dd_main_exit);
733 set_loop(zer_taken, loop->_parent);
734 // Plug in the true path
735 _igvn.hash_delete( post_head );
736 post_head->set_req(LoopNode::EntryControl, zer_taken);
737 set_idom(post_head, zer_taken, dd_main_exit);
738
739 // Step A3: Make the fall-in values to the post-loop come from the
740 // fall-out values of the main-loop.
741 for (DUIterator_Fast imax, i = main_head->fast_outs(imax); i < imax; i++) {
742 Node* main_phi = main_head->fast_out(i);
743 if( main_phi->is_Phi() && main_phi->in(0) == main_head && main_phi->outcnt() >0 ) {
744 Node *post_phi = old_new[main_phi->_idx];
745 Node *fallmain = clone_up_backedge_goo(main_head->back_control(),
746 post_head->init_control(),
747 main_phi->in(LoopNode::LoopBackControl));
748 _igvn.hash_delete(post_phi);
749 post_phi->set_req( LoopNode::EntryControl, fallmain );
750 }
751 }
752
753 // Update local caches for next stanza
754 main_exit = new_main_exit;
755
756
757 //------------------------------
758 // Step B: Create Pre-Loop.
759
760 // Step B1: Clone the loop body. The clone becomes the pre-loop. The main
761 // loop pre-header illegally has 2 control users (old & new loops).
762 clone_loop( loop, old_new, dd_main_head );
763 CountedLoopNode* pre_head = old_new[main_head->_idx]->as_CountedLoop();
764 CountedLoopEndNode* pre_end = old_new[main_end ->_idx]->as_CountedLoopEnd();
765 pre_head->set_pre_loop(main_head);
766 Node *pre_incr = old_new[incr->_idx];
767
768 // Reduce the pre-loop trip count.
769 pre_end->_prob = PROB_FAIR;
770
771 // Find the pre-loop normal exit.
772 Node* pre_exit = pre_end->proj_out(false);
773 assert( pre_exit->Opcode() == Op_IfFalse, "" );
774 IfFalseNode *new_pre_exit = new (C, 1) IfFalseNode(pre_end);
775 _igvn.register_new_node_with_optimizer( new_pre_exit );
776 set_idom(new_pre_exit, pre_end, dd_main_head);
777 set_loop(new_pre_exit, loop->_parent);
778
779 // Step B2: Build a zero-trip guard for the main-loop. After leaving the
780 // pre-loop, the main-loop may not execute at all. Later in life this
781 // zero-trip guard will become the minimum-trip guard when we unroll
782 // the main-loop.
783 Node *min_opaq = new (C, 2) Opaque1Node(C, limit);
784 Node *min_cmp = new (C, 3) CmpINode( pre_incr, min_opaq );
785 Node *min_bol = new (C, 2) BoolNode( min_cmp, b_test );
786 register_new_node( min_opaq, new_pre_exit );
787 register_new_node( min_cmp , new_pre_exit );
788 register_new_node( min_bol , new_pre_exit );
789
790 // Build the IfNode (assume the main-loop is executed always).
791 IfNode *min_iff = new (C, 2) IfNode( new_pre_exit, min_bol, PROB_ALWAYS, COUNT_UNKNOWN );
792 _igvn.register_new_node_with_optimizer( min_iff );
793 set_idom(min_iff, new_pre_exit, dd_main_head);
794 set_loop(min_iff, loop->_parent);
795
796 // Plug in the false-path, taken if we need to skip main-loop
797 _igvn.hash_delete( pre_exit );
798 pre_exit->set_req(0, min_iff);
799 set_idom(pre_exit, min_iff, dd_main_head);
800 set_idom(pre_exit->unique_out(), min_iff, dd_main_head);
801 // Make the true-path, must enter the main loop
802 Node *min_taken = new (C, 1) IfTrueNode( min_iff );
803 _igvn.register_new_node_with_optimizer( min_taken );
804 set_idom(min_taken, min_iff, dd_main_head);
805 set_loop(min_taken, loop->_parent);
806 // Plug in the true path
807 _igvn.hash_delete( main_head );
808 main_head->set_req(LoopNode::EntryControl, min_taken);
809 set_idom(main_head, min_taken, dd_main_head);
810
811 // Step B3: Make the fall-in values to the main-loop come from the
812 // fall-out values of the pre-loop.
813 for (DUIterator_Fast i2max, i2 = main_head->fast_outs(i2max); i2 < i2max; i2++) {
814 Node* main_phi = main_head->fast_out(i2);
815 if( main_phi->is_Phi() && main_phi->in(0) == main_head && main_phi->outcnt() > 0 ) {
816 Node *pre_phi = old_new[main_phi->_idx];
817 Node *fallpre = clone_up_backedge_goo(pre_head->back_control(),
818 main_head->init_control(),
819 pre_phi->in(LoopNode::LoopBackControl));
820 _igvn.hash_delete(main_phi);
821 main_phi->set_req( LoopNode::EntryControl, fallpre );
822 }
823 }
824
825 // Step B4: Shorten the pre-loop to run only 1 iteration (for now).
826 // RCE and alignment may change this later.
827 Node *cmp_end = pre_end->cmp_node();
828 assert( cmp_end->in(2) == limit, "" );
829 Node *pre_limit = new (C, 3) AddINode( init, stride );
830
831 // Save the original loop limit in this Opaque1 node for
832 // use by range check elimination.
833 Node *pre_opaq = new (C, 3) Opaque1Node(C, pre_limit, limit);
834
835 register_new_node( pre_limit, pre_head->in(0) );
836 register_new_node( pre_opaq , pre_head->in(0) );
837
838 // Since no other users of pre-loop compare, I can hack limit directly
839 assert( cmp_end->outcnt() == 1, "no other users" );
840 _igvn.hash_delete(cmp_end);
841 cmp_end->set_req(2, peel_only ? pre_limit : pre_opaq);
842
843 // Special case for not-equal loop bounds:
844 // Change pre loop test, main loop test, and the
845 // main loop guard test to use lt or gt depending on stride
846 // direction:
847 // positive stride use <
848 // negative stride use >
849
850 if (pre_end->in(CountedLoopEndNode::TestValue)->as_Bool()->_test._test == BoolTest::ne) {
851
852 BoolTest::mask new_test = (main_end->stride_con() > 0) ? BoolTest::lt : BoolTest::gt;
853 // Modify pre loop end condition
854 Node* pre_bol = pre_end->in(CountedLoopEndNode::TestValue)->as_Bool();
855 BoolNode* new_bol0 = new (C, 2) BoolNode(pre_bol->in(1), new_test);
856 register_new_node( new_bol0, pre_head->in(0) );
857 _igvn.hash_delete(pre_end);
858 pre_end->set_req(CountedLoopEndNode::TestValue, new_bol0);
859 // Modify main loop guard condition
860 assert(min_iff->in(CountedLoopEndNode::TestValue) == min_bol, "guard okay");
861 BoolNode* new_bol1 = new (C, 2) BoolNode(min_bol->in(1), new_test);
862 register_new_node( new_bol1, new_pre_exit );
863 _igvn.hash_delete(min_iff);
864 min_iff->set_req(CountedLoopEndNode::TestValue, new_bol1);
865 // Modify main loop end condition
866 BoolNode* main_bol = main_end->in(CountedLoopEndNode::TestValue)->as_Bool();
867 BoolNode* new_bol2 = new (C, 2) BoolNode(main_bol->in(1), new_test);
868 register_new_node( new_bol2, main_end->in(CountedLoopEndNode::TestControl) );
869 _igvn.hash_delete(main_end);
870 main_end->set_req(CountedLoopEndNode::TestValue, new_bol2);
871 }
872
873 // Flag main loop
874 main_head->set_main_loop();
875 if( peel_only ) main_head->set_main_no_pre_loop();
876
877 // It's difficult to be precise about the trip-counts
878 // for the pre/post loops. They are usually very short,
879 // so guess that 4 trips is a reasonable value.
880 post_head->set_profile_trip_cnt(4.0);
881 pre_head->set_profile_trip_cnt(4.0);
882
883 // Now force out all loop-invariant dominating tests. The optimizer
884 // finds some, but we _know_ they are all useless.
885 peeled_dom_test_elim(loop,old_new);
886 }
887
888 //------------------------------is_invariant-----------------------------
889 // Return true if n is invariant
890 bool IdealLoopTree::is_invariant(Node* n) const {
891 Node *n_c = _phase->has_ctrl(n) ? _phase->get_ctrl(n) : n;
892 if (n_c->is_top()) return false;
893 return !is_member(_phase->get_loop(n_c));
894 }
895
896
897 //------------------------------do_unroll--------------------------------------
898 // Unroll the loop body one step - make each trip do 2 iterations.
899 void PhaseIdealLoop::do_unroll( IdealLoopTree *loop, Node_List &old_new, bool adjust_min_trip ) {
900 assert( LoopUnrollLimit, "" );
901 #ifndef PRODUCT
902 if( PrintOpto && VerifyLoopOptimizations ) {
903 tty->print("Unrolling ");
904 loop->dump_head();
905 }
906 #endif
907 CountedLoopNode *loop_head = loop->_head->as_CountedLoop();
908 CountedLoopEndNode *loop_end = loop_head->loopexit();
909 assert( loop_end, "" );
910
911 // Remember loop node count before unrolling to detect
912 // if rounds of unroll,optimize are making progress
913 loop_head->set_node_count_before_unroll(loop->_body.size());
914
915 Node *ctrl = loop_head->in(LoopNode::EntryControl);
916 Node *limit = loop_head->limit();
917 Node *init = loop_head->init_trip();
918 Node *strid = loop_head->stride();
919
920 Node *opaq = NULL;
921 if( adjust_min_trip ) { // If not maximally unrolling, need adjustment
922 assert( loop_head->is_main_loop(), "" );
923 assert( ctrl->Opcode() == Op_IfTrue || ctrl->Opcode() == Op_IfFalse, "" );
924 Node *iff = ctrl->in(0);
925 assert( iff->Opcode() == Op_If, "" );
926 Node *bol = iff->in(1);
927 assert( bol->Opcode() == Op_Bool, "" );
928 Node *cmp = bol->in(1);
929 assert( cmp->Opcode() == Op_CmpI, "" );
930 opaq = cmp->in(2);
931 // Occasionally it's possible for a pre-loop Opaque1 node to be
932 // optimized away and then another round of loop opts attempted.
933 // We can not optimize this particular loop in that case.
934 if( opaq->Opcode() != Op_Opaque1 )
935 return; // Cannot find pre-loop! Bail out!
936 }
937
938 C->set_major_progress();
939
940 // Adjust max trip count. The trip count is intentionally rounded
941 // down here (e.g. 15-> 7-> 3-> 1) because if we unwittingly over-unroll,
942 // the main, unrolled, part of the loop will never execute as it is protected
943 // by the min-trip test. See bug 4834191 for a case where we over-unrolled
944 // and later determined that part of the unrolled loop was dead.
945 loop_head->set_trip_count(loop_head->trip_count() / 2);
946
947 // Double the count of original iterations in the unrolled loop body.
948 loop_head->double_unrolled_count();
949
950 // -----------
951 // Step 2: Cut back the trip counter for an unroll amount of 2.
952 // Loop will normally trip (limit - init)/stride_con. Since it's a
953 // CountedLoop this is exact (stride divides limit-init exactly).
954 // We are going to double the loop body, so we want to knock off any
955 // odd iteration: (trip_cnt & ~1). Then back compute a new limit.
956 Node *span = new (C, 3) SubINode( limit, init );
957 register_new_node( span, ctrl );
958 Node *trip = new (C, 3) DivINode( 0, span, strid );
959 register_new_node( trip, ctrl );
960 Node *mtwo = _igvn.intcon(-2);
961 set_ctrl(mtwo, C->root());
962 Node *rond = new (C, 3) AndINode( trip, mtwo );
963 register_new_node( rond, ctrl );
964 Node *spn2 = new (C, 3) MulINode( rond, strid );
965 register_new_node( spn2, ctrl );
966 Node *lim2 = new (C, 3) AddINode( spn2, init );
967 register_new_node( lim2, ctrl );
968
969 // Hammer in the new limit
970 Node *ctrl2 = loop_end->in(0);
971 Node *cmp2 = new (C, 3) CmpINode( loop_head->incr(), lim2 );
972 register_new_node( cmp2, ctrl2 );
973 Node *bol2 = new (C, 2) BoolNode( cmp2, loop_end->test_trip() );
974 register_new_node( bol2, ctrl2 );
975 _igvn.hash_delete(loop_end);
976 loop_end->set_req(CountedLoopEndNode::TestValue, bol2);
977
978 // Step 3: Find the min-trip test guaranteed before a 'main' loop.
979 // Make it a 1-trip test (means at least 2 trips).
980 if( adjust_min_trip ) {
981 // Guard test uses an 'opaque' node which is not shared. Hence I
982 // can edit it's inputs directly. Hammer in the new limit for the
983 // minimum-trip guard.
984 assert( opaq->outcnt() == 1, "" );
985 _igvn.hash_delete(opaq);
986 opaq->set_req(1, lim2);
987 }
988
989 // ---------
990 // Step 4: Clone the loop body. Move it inside the loop. This loop body
991 // represents the odd iterations; since the loop trips an even number of
992 // times its backedge is never taken. Kill the backedge.
993 uint dd = dom_depth(loop_head);
994 clone_loop( loop, old_new, dd );
995
996 // Make backedges of the clone equal to backedges of the original.
997 // Make the fall-in from the original come from the fall-out of the clone.
998 for (DUIterator_Fast jmax, j = loop_head->fast_outs(jmax); j < jmax; j++) {
999 Node* phi = loop_head->fast_out(j);
1000 if( phi->is_Phi() && phi->in(0) == loop_head && phi->outcnt() > 0 ) {
1001 Node *newphi = old_new[phi->_idx];
1002 _igvn.hash_delete( phi );
1003 _igvn.hash_delete( newphi );
1004
1005 phi ->set_req(LoopNode:: EntryControl, newphi->in(LoopNode::LoopBackControl));
1006 newphi->set_req(LoopNode::LoopBackControl, phi ->in(LoopNode::LoopBackControl));
1007 phi ->set_req(LoopNode::LoopBackControl, C->top());
1008 }
1009 }
1010 Node *clone_head = old_new[loop_head->_idx];
1011 _igvn.hash_delete( clone_head );
1012 loop_head ->set_req(LoopNode:: EntryControl, clone_head->in(LoopNode::LoopBackControl));
1013 clone_head->set_req(LoopNode::LoopBackControl, loop_head ->in(LoopNode::LoopBackControl));
1014 loop_head ->set_req(LoopNode::LoopBackControl, C->top());
1015 loop->_head = clone_head; // New loop header
1016
1017 set_idom(loop_head, loop_head ->in(LoopNode::EntryControl), dd);
1018 set_idom(clone_head, clone_head->in(LoopNode::EntryControl), dd);
1019
1020 // Kill the clone's backedge
1021 Node *newcle = old_new[loop_end->_idx];
1022 _igvn.hash_delete( newcle );
1023 Node *one = _igvn.intcon(1);
1024 set_ctrl(one, C->root());
1025 newcle->set_req(1, one);
1026 // Force clone into same loop body
1027 uint max = loop->_body.size();
1028 for( uint k = 0; k < max; k++ ) {
1029 Node *old = loop->_body.at(k);
1030 Node *nnn = old_new[old->_idx];
1031 loop->_body.push(nnn);
1032 if (!has_ctrl(old))
1033 set_loop(nnn, loop);
1034 }
1035
1036 loop->record_for_igvn();
1037 }
1038
1039 //------------------------------do_maximally_unroll----------------------------
1040
1041 void PhaseIdealLoop::do_maximally_unroll( IdealLoopTree *loop, Node_List &old_new ) {
1042 CountedLoopNode *cl = loop->_head->as_CountedLoop();
1043 assert( cl->trip_count() > 0, "");
1044
1045 // If loop is tripping an odd number of times, peel odd iteration
1046 if( (cl->trip_count() & 1) == 1 ) {
1047 do_peeling( loop, old_new );
1048 }
1049
1050 // Now its tripping an even number of times remaining. Double loop body.
1051 // Do not adjust pre-guards; they are not needed and do not exist.
1052 if( cl->trip_count() > 0 ) {
1053 do_unroll( loop, old_new, false );
1054 }
1055 }
1056
1057 //------------------------------dominates_backedge---------------------------------
1058 // Returns true if ctrl is executed on every complete iteration
1059 bool IdealLoopTree::dominates_backedge(Node* ctrl) {
1060 assert(ctrl->is_CFG(), "must be control");
1061 Node* backedge = _head->as_Loop()->in(LoopNode::LoopBackControl);
1062 return _phase->dom_lca_internal(ctrl, backedge) == ctrl;
1063 }
1064
1065 //------------------------------add_constraint---------------------------------
1066 // Constrain the main loop iterations so the condition:
1067 // scale_con * I + offset < limit
1068 // always holds true. That is, either increase the number of iterations in
1069 // the pre-loop or the post-loop until the condition holds true in the main
1070 // loop. Stride, scale, offset and limit are all loop invariant. Further,
1071 // stride and scale are constants (offset and limit often are).
1072 void PhaseIdealLoop::add_constraint( int stride_con, int scale_con, Node *offset, Node *limit, Node *pre_ctrl, Node **pre_limit, Node **main_limit ) {
1073
1074 // Compute "I :: (limit-offset)/scale_con"
1075 Node *con = new (C, 3) SubINode( limit, offset );
1076 register_new_node( con, pre_ctrl );
1077 Node *scale = _igvn.intcon(scale_con);
1078 set_ctrl(scale, C->root());
1079 Node *X = new (C, 3) DivINode( 0, con, scale );
1080 register_new_node( X, pre_ctrl );
1081
1082 // For positive stride, the pre-loop limit always uses a MAX function
1083 // and the main loop a MIN function. For negative stride these are
1084 // reversed.
1085
1086 // Also for positive stride*scale the affine function is increasing, so the
1087 // pre-loop must check for underflow and the post-loop for overflow.
1088 // Negative stride*scale reverses this; pre-loop checks for overflow and
1089 // post-loop for underflow.
1090 if( stride_con*scale_con > 0 ) {
1091 // Compute I < (limit-offset)/scale_con
1092 // Adjust main-loop last iteration to be MIN/MAX(main_loop,X)
1093 *main_limit = (stride_con > 0)
1094 ? (Node*)(new (C, 3) MinINode( *main_limit, X ))
1095 : (Node*)(new (C, 3) MaxINode( *main_limit, X ));
1096 register_new_node( *main_limit, pre_ctrl );
1097
1098 } else {
1099 // Compute (limit-offset)/scale_con + SGN(-scale_con) <= I
1100 // Add the negation of the main-loop constraint to the pre-loop.
1101 // See footnote [++] below for a derivation of the limit expression.
1102 Node *incr = _igvn.intcon(scale_con > 0 ? -1 : 1);
1103 set_ctrl(incr, C->root());
1104 Node *adj = new (C, 3) AddINode( X, incr );
1105 register_new_node( adj, pre_ctrl );
1106 *pre_limit = (scale_con > 0)
1107 ? (Node*)new (C, 3) MinINode( *pre_limit, adj )
1108 : (Node*)new (C, 3) MaxINode( *pre_limit, adj );
1109 register_new_node( *pre_limit, pre_ctrl );
1110
1111 // [++] Here's the algebra that justifies the pre-loop limit expression:
1112 //
1113 // NOT( scale_con * I + offset < limit )
1114 // ==
1115 // scale_con * I + offset >= limit
1116 // ==
1117 // SGN(scale_con) * I >= (limit-offset)/|scale_con|
1118 // ==
1119 // (limit-offset)/|scale_con| <= I * SGN(scale_con)
1120 // ==
1121 // (limit-offset)/|scale_con|-1 < I * SGN(scale_con)
1122 // ==
1123 // ( if (scale_con > 0) /*common case*/
1124 // (limit-offset)/scale_con - 1 < I
1125 // else
1126 // (limit-offset)/scale_con + 1 > I
1127 // )
1128 // ( if (scale_con > 0) /*common case*/
1129 // (limit-offset)/scale_con + SGN(-scale_con) < I
1130 // else
1131 // (limit-offset)/scale_con + SGN(-scale_con) > I
1132 }
1133 }
1134
1135
1136 //------------------------------is_scaled_iv---------------------------------
1137 // Return true if exp is a constant times an induction var
1138 bool PhaseIdealLoop::is_scaled_iv(Node* exp, Node* iv, int* p_scale) {
1139 if (exp == iv) {
1140 if (p_scale != NULL) {
1141 *p_scale = 1;
1142 }
1143 return true;
1144 }
1145 int opc = exp->Opcode();
1146 if (opc == Op_MulI) {
1147 if (exp->in(1) == iv && exp->in(2)->is_Con()) {
1148 if (p_scale != NULL) {
1149 *p_scale = exp->in(2)->get_int();
1150 }
1151 return true;
1152 }
1153 if (exp->in(2) == iv && exp->in(1)->is_Con()) {
1154 if (p_scale != NULL) {
1155 *p_scale = exp->in(1)->get_int();
1156 }
1157 return true;
1158 }
1159 } else if (opc == Op_LShiftI) {
1160 if (exp->in(1) == iv && exp->in(2)->is_Con()) {
1161 if (p_scale != NULL) {
1162 *p_scale = 1 << exp->in(2)->get_int();
1163 }
1164 return true;
1165 }
1166 }
1167 return false;
1168 }
1169
1170 //-----------------------------is_scaled_iv_plus_offset------------------------------
1171 // Return true if exp is a simple induction variable expression: k1*iv + (invar + k2)
1172 bool PhaseIdealLoop::is_scaled_iv_plus_offset(Node* exp, Node* iv, int* p_scale, Node** p_offset, int depth) {
1173 if (is_scaled_iv(exp, iv, p_scale)) {
1174 if (p_offset != NULL) {
1175 Node *zero = _igvn.intcon(0);
1176 set_ctrl(zero, C->root());
1177 *p_offset = zero;
1178 }
1179 return true;
1180 }
1181 int opc = exp->Opcode();
1182 if (opc == Op_AddI) {
1183 if (is_scaled_iv(exp->in(1), iv, p_scale)) {
1184 if (p_offset != NULL) {
1185 *p_offset = exp->in(2);
1186 }
1187 return true;
1188 }
1189 if (exp->in(2)->is_Con()) {
1190 Node* offset2 = NULL;
1191 if (depth < 2 &&
1192 is_scaled_iv_plus_offset(exp->in(1), iv, p_scale,
1193 p_offset != NULL ? &offset2 : NULL, depth+1)) {
1194 if (p_offset != NULL) {
1195 Node *ctrl_off2 = get_ctrl(offset2);
1196 Node* offset = new (C, 3) AddINode(offset2, exp->in(2));
1197 register_new_node(offset, ctrl_off2);
1198 *p_offset = offset;
1199 }
1200 return true;
1201 }
1202 }
1203 } else if (opc == Op_SubI) {
1204 if (is_scaled_iv(exp->in(1), iv, p_scale)) {
1205 if (p_offset != NULL) {
1206 Node *zero = _igvn.intcon(0);
1207 set_ctrl(zero, C->root());
1208 Node *ctrl_off = get_ctrl(exp->in(2));
1209 Node* offset = new (C, 3) SubINode(zero, exp->in(2));
1210 register_new_node(offset, ctrl_off);
1211 *p_offset = offset;
1212 }
1213 return true;
1214 }
1215 if (is_scaled_iv(exp->in(2), iv, p_scale)) {
1216 if (p_offset != NULL) {
1217 *p_scale *= -1;
1218 *p_offset = exp->in(1);
1219 }
1220 return true;
1221 }
1222 }
1223 return false;
1224 }
1225
1226 //------------------------------do_range_check---------------------------------
1227 // Eliminate range-checks and other trip-counter vs loop-invariant tests.
1228 void PhaseIdealLoop::do_range_check( IdealLoopTree *loop, Node_List &old_new ) {
1229 #ifndef PRODUCT
1230 if( PrintOpto && VerifyLoopOptimizations ) {
1231 tty->print("Range Check Elimination ");
1232 loop->dump_head();
1233 }
1234 #endif
1235 assert( RangeCheckElimination, "" );
1236 CountedLoopNode *cl = loop->_head->as_CountedLoop();
1237 assert( cl->is_main_loop(), "" );
1238
1239 // Find the trip counter; we are iteration splitting based on it
1240 Node *trip_counter = cl->phi();
1241 // Find the main loop limit; we will trim it's iterations
1242 // to not ever trip end tests
1243 Node *main_limit = cl->limit();
1244 // Find the pre-loop limit; we will expand it's iterations to
1245 // not ever trip low tests.
1246 Node *ctrl = cl->in(LoopNode::EntryControl);
1247 assert( ctrl->Opcode() == Op_IfTrue || ctrl->Opcode() == Op_IfFalse, "" );
1248 Node *iffm = ctrl->in(0);
1249 assert( iffm->Opcode() == Op_If, "" );
1250 Node *p_f = iffm->in(0);
1251 assert( p_f->Opcode() == Op_IfFalse, "" );
1252 CountedLoopEndNode *pre_end = p_f->in(0)->as_CountedLoopEnd();
1253 assert( pre_end->loopnode()->is_pre_loop(), "" );
1254 Node *pre_opaq1 = pre_end->limit();
1255 // Occasionally it's possible for a pre-loop Opaque1 node to be
1256 // optimized away and then another round of loop opts attempted.
1257 // We can not optimize this particular loop in that case.
1258 if( pre_opaq1->Opcode() != Op_Opaque1 )
1259 return;
1260 Opaque1Node *pre_opaq = (Opaque1Node*)pre_opaq1;
1261 Node *pre_limit = pre_opaq->in(1);
1262
1263 // Where do we put new limit calculations
1264 Node *pre_ctrl = pre_end->loopnode()->in(LoopNode::EntryControl);
1265
1266 // Ensure the original loop limit is available from the
1267 // pre-loop Opaque1 node.
1268 Node *orig_limit = pre_opaq->original_loop_limit();
1269 if( orig_limit == NULL || _igvn.type(orig_limit) == Type::TOP )
1270 return;
1271
1272 // Need to find the main-loop zero-trip guard
1273 Node *bolzm = iffm->in(1);
1274 assert( bolzm->Opcode() == Op_Bool, "" );
1275 Node *cmpzm = bolzm->in(1);
1276 assert( cmpzm->is_Cmp(), "" );
1277 Node *opqzm = cmpzm->in(2);
1278 if( opqzm->Opcode() != Op_Opaque1 )
1279 return;
1280 assert( opqzm->in(1) == main_limit, "do not understand situation" );
1281
1282 // Must know if its a count-up or count-down loop
1283
1284 // protect against stride not being a constant
1285 if ( !cl->stride_is_con() ) {
1286 return;
1287 }
1288 int stride_con = cl->stride_con();
1289 Node *zero = _igvn.intcon(0);
1290 Node *one = _igvn.intcon(1);
1291 set_ctrl(zero, C->root());
1292 set_ctrl(one, C->root());
1293
1294 // Range checks that do not dominate the loop backedge (ie.
1295 // conditionally executed) can lengthen the pre loop limit beyond
1296 // the original loop limit. To prevent this, the pre limit is
1297 // (for stride > 0) MINed with the original loop limit (MAXed
1298 // stride < 0) when some range_check (rc) is conditionally
1299 // executed.
1300 bool conditional_rc = false;
1301
1302 // Check loop body for tests of trip-counter plus loop-invariant vs
1303 // loop-invariant.
1304 for( uint i = 0; i < loop->_body.size(); i++ ) {
1305 Node *iff = loop->_body[i];
1306 if( iff->Opcode() == Op_If ) { // Test?
1307
1308 // Test is an IfNode, has 2 projections. If BOTH are in the loop
1309 // we need loop unswitching instead of iteration splitting.
1310 Node *exit = loop->is_loop_exit(iff);
1311 if( !exit ) continue;
1312 int flip = (exit->Opcode() == Op_IfTrue) ? 1 : 0;
1313
1314 // Get boolean condition to test
1315 Node *i1 = iff->in(1);
1316 if( !i1->is_Bool() ) continue;
1317 BoolNode *bol = i1->as_Bool();
1318 BoolTest b_test = bol->_test;
1319 // Flip sense of test if exit condition is flipped
1320 if( flip )
1321 b_test = b_test.negate();
1322
1323 // Get compare
1324 Node *cmp = bol->in(1);
1325
1326 // Look for trip_counter + offset vs limit
1327 Node *rc_exp = cmp->in(1);
1328 Node *limit = cmp->in(2);
1329 jint scale_con= 1; // Assume trip counter not scaled
1330
1331 Node *limit_c = get_ctrl(limit);
1332 if( loop->is_member(get_loop(limit_c) ) ) {
1333 // Compare might have operands swapped; commute them
1334 b_test = b_test.commute();
1335 rc_exp = cmp->in(2);
1336 limit = cmp->in(1);
1337 limit_c = get_ctrl(limit);
1338 if( loop->is_member(get_loop(limit_c) ) )
1339 continue; // Both inputs are loop varying; cannot RCE
1340 }
1341 // Here we know 'limit' is loop invariant
1342
1343 // 'limit' maybe pinned below the zero trip test (probably from a
1344 // previous round of rce), in which case, it can't be used in the
1345 // zero trip test expression which must occur before the zero test's if.
1346 if( limit_c == ctrl ) {
1347 continue; // Don't rce this check but continue looking for other candidates.
1348 }
1349
1350 // Check for scaled induction variable plus an offset
1351 Node *offset = NULL;
1352
1353 if (!is_scaled_iv_plus_offset(rc_exp, trip_counter, &scale_con, &offset)) {
1354 continue;
1355 }
1356
1357 Node *offset_c = get_ctrl(offset);
1358 if( loop->is_member( get_loop(offset_c) ) )
1359 continue; // Offset is not really loop invariant
1360 // Here we know 'offset' is loop invariant.
1361
1362 // As above for the 'limit', the 'offset' maybe pinned below the
1363 // zero trip test.
1364 if( offset_c == ctrl ) {
1365 continue; // Don't rce this check but continue looking for other candidates.
1366 }
1367
1368 // At this point we have the expression as:
1369 // scale_con * trip_counter + offset :: limit
1370 // where scale_con, offset and limit are loop invariant. Trip_counter
1371 // monotonically increases by stride_con, a constant. Both (or either)
1372 // stride_con and scale_con can be negative which will flip about the
1373 // sense of the test.
1374
1375 // Adjust pre and main loop limits to guard the correct iteration set
1376 if( cmp->Opcode() == Op_CmpU ) {// Unsigned compare is really 2 tests
1377 if( b_test._test == BoolTest::lt ) { // Range checks always use lt
1378 // The overflow limit: scale*I+offset < limit
1379 add_constraint( stride_con, scale_con, offset, limit, pre_ctrl, &pre_limit, &main_limit );
1380 // The underflow limit: 0 <= scale*I+offset.
1381 // Some math yields: -scale*I-(offset+1) < 0
1382 Node *plus_one = new (C, 3) AddINode( offset, one );
1383 register_new_node( plus_one, pre_ctrl );
1384 Node *neg_offset = new (C, 3) SubINode( zero, plus_one );
1385 register_new_node( neg_offset, pre_ctrl );
1386 add_constraint( stride_con, -scale_con, neg_offset, zero, pre_ctrl, &pre_limit, &main_limit );
1387 if (!conditional_rc) {
1388 conditional_rc = !loop->dominates_backedge(iff);
1389 }
1390 } else {
1391 #ifndef PRODUCT
1392 if( PrintOpto )
1393 tty->print_cr("missed RCE opportunity");
1394 #endif
1395 continue; // In release mode, ignore it
1396 }
1397 } else { // Otherwise work on normal compares
1398 switch( b_test._test ) {
1399 case BoolTest::ge: // Convert X >= Y to -X <= -Y
1400 scale_con = -scale_con;
1401 offset = new (C, 3) SubINode( zero, offset );
1402 register_new_node( offset, pre_ctrl );
1403 limit = new (C, 3) SubINode( zero, limit );
1404 register_new_node( limit, pre_ctrl );
1405 // Fall into LE case
1406 case BoolTest::le: // Convert X <= Y to X < Y+1
1407 limit = new (C, 3) AddINode( limit, one );
1408 register_new_node( limit, pre_ctrl );
1409 // Fall into LT case
1410 case BoolTest::lt:
1411 add_constraint( stride_con, scale_con, offset, limit, pre_ctrl, &pre_limit, &main_limit );
1412 if (!conditional_rc) {
1413 conditional_rc = !loop->dominates_backedge(iff);
1414 }
1415 break;
1416 default:
1417 #ifndef PRODUCT
1418 if( PrintOpto )
1419 tty->print_cr("missed RCE opportunity");
1420 #endif
1421 continue; // Unhandled case
1422 }
1423 }
1424
1425 // Kill the eliminated test
1426 C->set_major_progress();
1427 Node *kill_con = _igvn.intcon( 1-flip );
1428 set_ctrl(kill_con, C->root());
1429 _igvn.hash_delete(iff);
1430 iff->set_req(1, kill_con);
1431 _igvn._worklist.push(iff);
1432 // Find surviving projection
1433 assert(iff->is_If(), "");
1434 ProjNode* dp = ((IfNode*)iff)->proj_out(1-flip);
1435 // Find loads off the surviving projection; remove their control edge
1436 for (DUIterator_Fast imax, i = dp->fast_outs(imax); i < imax; i++) {
1437 Node* cd = dp->fast_out(i); // Control-dependent node
1438 if( cd->is_Load() ) { // Loads can now float around in the loop
1439 _igvn.hash_delete(cd);
1440 // Allow the load to float around in the loop, or before it
1441 // but NOT before the pre-loop.
1442 cd->set_req(0, ctrl); // ctrl, not NULL
1443 _igvn._worklist.push(cd);
1444 --i;
1445 --imax;
1446 }
1447 }
1448
1449 } // End of is IF
1450
1451 }
1452
1453 // Update loop limits
1454 if (conditional_rc) {
1455 pre_limit = (stride_con > 0) ? (Node*)new (C,3) MinINode(pre_limit, orig_limit)
1456 : (Node*)new (C,3) MaxINode(pre_limit, orig_limit);
1457 register_new_node(pre_limit, pre_ctrl);
1458 }
1459 _igvn.hash_delete(pre_opaq);
1460 pre_opaq->set_req(1, pre_limit);
1461
1462 // Note:: we are making the main loop limit no longer precise;
1463 // need to round up based on stride.
1464 if( stride_con != 1 && stride_con != -1 ) { // Cutout for common case
1465 // "Standard" round-up logic: ([main_limit-init+(y-1)]/y)*y+init
1466 // Hopefully, compiler will optimize for powers of 2.
1467 Node *ctrl = get_ctrl(main_limit);
1468 Node *stride = cl->stride();
1469 Node *init = cl->init_trip();
1470 Node *span = new (C, 3) SubINode(main_limit,init);
1471 register_new_node(span,ctrl);
1472 Node *rndup = _igvn.intcon(stride_con + ((stride_con>0)?-1:1));
1473 Node *add = new (C, 3) AddINode(span,rndup);
1474 register_new_node(add,ctrl);
1475 Node *div = new (C, 3) DivINode(0,add,stride);
1476 register_new_node(div,ctrl);
1477 Node *mul = new (C, 3) MulINode(div,stride);
1478 register_new_node(mul,ctrl);
1479 Node *newlim = new (C, 3) AddINode(mul,init);
1480 register_new_node(newlim,ctrl);
1481 main_limit = newlim;
1482 }
1483
1484 Node *main_cle = cl->loopexit();
1485 Node *main_bol = main_cle->in(1);
1486 // Hacking loop bounds; need private copies of exit test
1487 if( main_bol->outcnt() > 1 ) {// BoolNode shared?
1488 _igvn.hash_delete(main_cle);
1489 main_bol = main_bol->clone();// Clone a private BoolNode
1490 register_new_node( main_bol, main_cle->in(0) );
1491 main_cle->set_req(1,main_bol);
1492 }
1493 Node *main_cmp = main_bol->in(1);
1494 if( main_cmp->outcnt() > 1 ) { // CmpNode shared?
1495 _igvn.hash_delete(main_bol);
1496 main_cmp = main_cmp->clone();// Clone a private CmpNode
1497 register_new_node( main_cmp, main_cle->in(0) );
1498 main_bol->set_req(1,main_cmp);
1499 }
1500 // Hack the now-private loop bounds
1501 _igvn.hash_delete(main_cmp);
1502 main_cmp->set_req(2, main_limit);
1503 _igvn._worklist.push(main_cmp);
1504 // The OpaqueNode is unshared by design
1505 _igvn.hash_delete(opqzm);
1506 assert( opqzm->outcnt() == 1, "cannot hack shared node" );
1507 opqzm->set_req(1,main_limit);
1508 _igvn._worklist.push(opqzm);
1509 }
1510
1511 //------------------------------DCE_loop_body----------------------------------
1512 // Remove simplistic dead code from loop body
1513 void IdealLoopTree::DCE_loop_body() {
1514 for( uint i = 0; i < _body.size(); i++ )
1515 if( _body.at(i)->outcnt() == 0 )
1516 _body.map( i--, _body.pop() );
1517 }
1518
1519
1520 //------------------------------adjust_loop_exit_prob--------------------------
1521 // Look for loop-exit tests with the 50/50 (or worse) guesses from the parsing stage.
1522 // Replace with a 1-in-10 exit guess.
1523 void IdealLoopTree::adjust_loop_exit_prob( PhaseIdealLoop *phase ) {
1524 Node *test = tail();
1525 while( test != _head ) {
1526 uint top = test->Opcode();
1527 if( top == Op_IfTrue || top == Op_IfFalse ) {
1528 int test_con = ((ProjNode*)test)->_con;
1529 assert(top == (uint)(test_con? Op_IfTrue: Op_IfFalse), "sanity");
1530 IfNode *iff = test->in(0)->as_If();
1531 if( iff->outcnt() == 2 ) { // Ignore dead tests
1532 Node *bol = iff->in(1);
1533 if( bol && bol->req() > 1 && bol->in(1) &&
1534 ((bol->in(1)->Opcode() == Op_StorePConditional ) ||
1535 (bol->in(1)->Opcode() == Op_StoreIConditional ) ||
1536 (bol->in(1)->Opcode() == Op_StoreLConditional ) ||
1537 (bol->in(1)->Opcode() == Op_CompareAndSwapI ) ||
1538 (bol->in(1)->Opcode() == Op_CompareAndSwapL ) ||
1539 (bol->in(1)->Opcode() == Op_CompareAndSwapP ) ||
1540 (bol->in(1)->Opcode() == Op_CompareAndSwapN )))
1541 return; // Allocation loops RARELY take backedge
1542 // Find the OTHER exit path from the IF
1543 Node* ex = iff->proj_out(1-test_con);
1544 float p = iff->_prob;
1545 if( !phase->is_member( this, ex ) && iff->_fcnt == COUNT_UNKNOWN ) {
1546 if( top == Op_IfTrue ) {
1547 if( p < (PROB_FAIR + PROB_UNLIKELY_MAG(3))) {
1548 iff->_prob = PROB_STATIC_FREQUENT;
1549 }
1550 } else {
1551 if( p > (PROB_FAIR - PROB_UNLIKELY_MAG(3))) {
1552 iff->_prob = PROB_STATIC_INFREQUENT;
1553 }
1554 }
1555 }
1556 }
1557 }
1558 test = phase->idom(test);
1559 }
1560 }
1561
1562
1563 //------------------------------policy_do_remove_empty_loop--------------------
1564 // Micro-benchmark spamming. Policy is to always remove empty loops.
1565 // The 'DO' part is to replace the trip counter with the value it will
1566 // have on the last iteration. This will break the loop.
1567 bool IdealLoopTree::policy_do_remove_empty_loop( PhaseIdealLoop *phase ) {
1568 // Minimum size must be empty loop
1569 if( _body.size() > 7/*number of nodes in an empty loop*/ ) return false;
1570
1571 if( !_head->is_CountedLoop() ) return false; // Dead loop
1572 CountedLoopNode *cl = _head->as_CountedLoop();
1573 if( !cl->loopexit() ) return false; // Malformed loop
1574 if( !phase->is_member(this,phase->get_ctrl(cl->loopexit()->in(CountedLoopEndNode::TestValue)) ) )
1575 return false; // Infinite loop
1576 #ifndef PRODUCT
1577 if( PrintOpto )
1578 tty->print_cr("Removing empty loop");
1579 #endif
1580 #ifdef ASSERT
1581 // Ensure only one phi which is the iv.
1582 Node* iv = NULL;
1583 for (DUIterator_Fast imax, i = cl->fast_outs(imax); i < imax; i++) {
1584 Node* n = cl->fast_out(i);
1585 if (n->Opcode() == Op_Phi) {
1586 assert(iv == NULL, "Too many phis" );
1587 iv = n;
1588 }
1589 }
1590 assert(iv == cl->phi(), "Wrong phi" );
1591 #endif
1592 // Replace the phi at loop head with the final value of the last
1593 // iteration. Then the CountedLoopEnd will collapse (backedge never
1594 // taken) and all loop-invariant uses of the exit values will be correct.
1595 Node *phi = cl->phi();
1596 Node *final = new (phase->C, 3) SubINode( cl->limit(), cl->stride() );
1597 phase->register_new_node(final,cl->in(LoopNode::EntryControl));
1598 phase->_igvn.replace_node(phi,final);
1599 phase->C->set_major_progress();
1600 return true;
1601 }
1602
1603
1604 //=============================================================================
1605 //------------------------------iteration_split_impl---------------------------
1606 bool IdealLoopTree::iteration_split_impl( PhaseIdealLoop *phase, Node_List &old_new ) {
1607 // Check and remove empty loops (spam micro-benchmarks)
1608 if( policy_do_remove_empty_loop(phase) )
1609 return true; // Here we removed an empty loop
1610
1611 bool should_peel = policy_peeling(phase); // Should we peel?
1612
1613 bool should_unswitch = policy_unswitching(phase);
1614
1615 // Non-counted loops may be peeled; exactly 1 iteration is peeled.
1616 // This removes loop-invariant tests (usually null checks).
1617 if( !_head->is_CountedLoop() ) { // Non-counted loop
1618 if (PartialPeelLoop && phase->partial_peel(this, old_new)) {
1619 // Partial peel succeeded so terminate this round of loop opts
1620 return false;
1621 }
1622 if( should_peel ) { // Should we peel?
1623 #ifndef PRODUCT
1624 if (PrintOpto) tty->print_cr("should_peel");
1625 #endif
1626 phase->do_peeling(this,old_new);
1627 } else if( should_unswitch ) {
1628 phase->do_unswitching(this, old_new);
1629 }
1630 return true;
1631 }
1632 CountedLoopNode *cl = _head->as_CountedLoop();
1633
1634 if( !cl->loopexit() ) return true; // Ignore various kinds of broken loops
1635
1636 // Do nothing special to pre- and post- loops
1637 if( cl->is_pre_loop() || cl->is_post_loop() ) return true;
1638
1639 // Compute loop trip count from profile data
1640 compute_profile_trip_cnt(phase);
1641
1642 // Before attempting fancy unrolling, RCE or alignment, see if we want
1643 // to completely unroll this loop or do loop unswitching.
1644 if( cl->is_normal_loop() ) {
1645 if (should_unswitch) {
1646 phase->do_unswitching(this, old_new);
1647 return true;
1648 }
1649 bool should_maximally_unroll = policy_maximally_unroll(phase);
1650 if( should_maximally_unroll ) {
1651 // Here we did some unrolling and peeling. Eventually we will
1652 // completely unroll this loop and it will no longer be a loop.
1653 phase->do_maximally_unroll(this,old_new);
1654 return true;
1655 }
1656 }
1657
1658
1659 // Counted loops may be peeled, may need some iterations run up
1660 // front for RCE, and may want to align loop refs to a cache
1661 // line. Thus we clone a full loop up front whose trip count is
1662 // at least 1 (if peeling), but may be several more.
1663
1664 // The main loop will start cache-line aligned with at least 1
1665 // iteration of the unrolled body (zero-trip test required) and
1666 // will have some range checks removed.
1667
1668 // A post-loop will finish any odd iterations (leftover after
1669 // unrolling), plus any needed for RCE purposes.
1670
1671 bool should_unroll = policy_unroll(phase);
1672
1673 bool should_rce = policy_range_check(phase);
1674
1675 bool should_align = policy_align(phase);
1676
1677 // If not RCE'ing (iteration splitting) or Aligning, then we do not
1678 // need a pre-loop. We may still need to peel an initial iteration but
1679 // we will not be needing an unknown number of pre-iterations.
1680 //
1681 // Basically, if may_rce_align reports FALSE first time through,
1682 // we will not be able to later do RCE or Aligning on this loop.
1683 bool may_rce_align = !policy_peel_only(phase) || should_rce || should_align;
1684
1685 // If we have any of these conditions (RCE, alignment, unrolling) met, then
1686 // we switch to the pre-/main-/post-loop model. This model also covers
1687 // peeling.
1688 if( should_rce || should_align || should_unroll ) {
1689 if( cl->is_normal_loop() ) // Convert to 'pre/main/post' loops
1690 phase->insert_pre_post_loops(this,old_new, !may_rce_align);
1691
1692 // Adjust the pre- and main-loop limits to let the pre and post loops run
1693 // with full checks, but the main-loop with no checks. Remove said
1694 // checks from the main body.
1695 if( should_rce )
1696 phase->do_range_check(this,old_new);
1697
1698 // Double loop body for unrolling. Adjust the minimum-trip test (will do
1699 // twice as many iterations as before) and the main body limit (only do
1700 // an even number of trips). If we are peeling, we might enable some RCE
1701 // and we'd rather unroll the post-RCE'd loop SO... do not unroll if
1702 // peeling.
1703 if( should_unroll && !should_peel )
1704 phase->do_unroll(this,old_new, true);
1705
1706 // Adjust the pre-loop limits to align the main body
1707 // iterations.
1708 if( should_align )
1709 Unimplemented();
1710
1711 } else { // Else we have an unchanged counted loop
1712 if( should_peel ) // Might want to peel but do nothing else
1713 phase->do_peeling(this,old_new);
1714 }
1715 return true;
1716 }
1717
1718
1719 //=============================================================================
1720 //------------------------------iteration_split--------------------------------
1721 bool IdealLoopTree::iteration_split( PhaseIdealLoop *phase, Node_List &old_new ) {
1722 // Recursively iteration split nested loops
1723 if( _child && !_child->iteration_split( phase, old_new ))
1724 return false;
1725
1726 // Clean out prior deadwood
1727 DCE_loop_body();
1728
1729
1730 // Look for loop-exit tests with my 50/50 guesses from the Parsing stage.
1731 // Replace with a 1-in-10 exit guess.
1732 if( _parent /*not the root loop*/ &&
1733 !_irreducible &&
1734 // Also ignore the occasional dead backedge
1735 !tail()->is_top() ) {
1736 adjust_loop_exit_prob(phase);
1737 }
1738
1739
1740 // Gate unrolling, RCE and peeling efforts.
1741 if( !_child && // If not an inner loop, do not split
1742 !_irreducible &&
1743 _allow_optimizations &&
1744 !tail()->is_top() ) { // Also ignore the occasional dead backedge
1745 if (!_has_call) {
1746 if (!iteration_split_impl( phase, old_new )) {
1747 return false;
1748 }
1749 } else if (policy_unswitching(phase)) {
1750 phase->do_unswitching(this, old_new);
1751 }
1752 }
1753
1754 // Minor offset re-organization to remove loop-fallout uses of
1755 // trip counter.
1756 if( _head->is_CountedLoop() ) phase->reorg_offsets( this );
1757 if( _next && !_next->iteration_split( phase, old_new ))
1758 return false;
1759 return true;
1760 }
1761
1762 //-------------------------------is_uncommon_trap_proj----------------------------
1763 // Return true if proj is the form of "proj->[region->..]call_uct"
1764 bool PhaseIdealLoop::is_uncommon_trap_proj(ProjNode* proj, bool must_reason_predicate) {
1765 int path_limit = 10;
1766 assert(proj, "invalid argument");
1767 Node* out = proj;
1768 for (int ct = 0; ct < path_limit; ct++) {
1769 out = out->unique_ctrl_out();
1770 if (out == NULL || out->is_Root() || out->is_Start())
1771 return false;
1772 if (out->is_CallStaticJava()) {
1773 int req = out->as_CallStaticJava()->uncommon_trap_request();
1774 if (req != 0) {
1775 Deoptimization::DeoptReason reason = Deoptimization::trap_request_reason(req);
1776 if (!must_reason_predicate || reason == Deoptimization::Reason_predicate){
1777 return true;
1778 }
1779 }
1780 return false; // don't do further after call
1781 }
1782 }
1783 return false;
1784 }
1785
1786 //-------------------------------is_uncommon_trap_if_pattern-------------------------
1787 // Return true for "if(test)-> proj -> ...
1788 // |
1789 // V
1790 // other_proj->[region->..]call_uct"
1791 //
1792 // "must_reason_predicate" means the uct reason must be Reason_predicate
1793 bool PhaseIdealLoop::is_uncommon_trap_if_pattern(ProjNode *proj, bool must_reason_predicate) {
1794 Node *in0 = proj->in(0);
1795 if (!in0->is_If()) return false;
1796 // Variation of a dead If node.
1797 if (in0->outcnt() < 2) return false;
1798 IfNode* iff = in0->as_If();
1799
1800 // we need "If(Conv2B(Opaque1(...)))" pattern for must_reason_predicate
1801 if (must_reason_predicate) {
1802 if (iff->in(1)->Opcode() != Op_Conv2B ||
1803 iff->in(1)->in(1)->Opcode() != Op_Opaque1) {
1804 return false;
1805 }
1806 }
1807
1808 ProjNode* other_proj = iff->proj_out(1-proj->_con)->as_Proj();
1809 return is_uncommon_trap_proj(other_proj, must_reason_predicate);
1810 }
1811
1812 //------------------------------create_new_if_for_predicate------------------------
1813 // create a new if above the uct_if_pattern for the predicate to be promoted.
1814 //
1815 // before after
1816 // ---------- ----------
1817 // ctrl ctrl
1818 // | |
1819 // | |
1820 // v v
1821 // iff new_iff
1822 // / \ / \
1823 // / \ / \
1824 // v v v v
1825 // uncommon_proj cont_proj if_uct if_cont
1826 // \ | | | |
1827 // \ | | | |
1828 // v v v | v
1829 // rgn loop | iff
1830 // | | / \
1831 // | | / \
1832 // v | v v
1833 // uncommon_trap | uncommon_proj cont_proj
1834 // \ \ | |
1835 // \ \ | |
1836 // v v v v
1837 // rgn loop
1838 // |
1839 // |
1840 // v
1841 // uncommon_trap
1842 //
1843 //
1844 // We will create a region to guard the uct call if there is no one there.
1845 // The true projecttion (if_cont) of the new_iff is returned.
1846 ProjNode* PhaseIdealLoop::create_new_if_for_predicate(ProjNode* cont_proj) {
1847 assert(is_uncommon_trap_if_pattern(cont_proj, true), "must be a uct if pattern!");
1848 IfNode* iff = cont_proj->in(0)->as_If();
1849
1850 ProjNode *uncommon_proj = iff->proj_out(1 - cont_proj->_con);
1851 Node *rgn = uncommon_proj->unique_ctrl_out();
1852 assert(rgn->is_Region() || rgn->is_Call(), "must be a region or call uct");
1853
1854 if (!rgn->is_Region()) { // create a region to guard the call
1855 assert(rgn->is_Call(), "must be call uct");
1856 CallNode* call = rgn->as_Call();
1857 rgn = new (C, 1) RegionNode(1);
1858 _igvn.set_type(rgn, rgn->bottom_type());
1859 rgn->add_req(uncommon_proj);
1860 set_idom(rgn, idom(uncommon_proj), dom_depth(uncommon_proj)+1);
1861 _igvn.hash_delete(call);
1862 call->set_req(0, rgn);
1863 }
1864
1865 // Create new_iff
1866 uint iffdd = dom_depth(iff);
1867 IdealLoopTree* lp = get_loop(iff);
1868 IfNode *new_iff = new (C, 2) IfNode(iff->in(0), NULL, iff->_prob, iff->_fcnt);
1869 register_node(new_iff, lp, idom(iff), iffdd);
1870 Node *if_cont = new (C, 1) IfTrueNode(new_iff);
1871 Node *if_uct = new (C, 1) IfFalseNode(new_iff);
1872 if (cont_proj->is_IfFalse()) {
1873 // Swap
1874 Node* tmp = if_uct; if_uct = if_cont; if_cont = tmp;
1875 }
1876 register_node(if_cont, lp, new_iff, iffdd);
1877 register_node(if_uct, get_loop(rgn), new_iff, iffdd);
1878
1879 // if_cont to iff
1880 _igvn.hash_delete(iff);
1881 iff->set_req(0, if_cont);
1882 set_idom(iff, if_cont, dom_depth(iff));
1883
1884 // if_uct to rgn
1885 _igvn.hash_delete(rgn);
1886 rgn->add_req(if_uct);
1887 Node* ridom = idom(rgn);
1888 Node* nrdom = dom_lca(ridom, new_iff);
1889 set_idom(rgn, nrdom, dom_depth(rgn));
1890
1891 // rgn must have no phis
1892 assert(!rgn->as_Region()->has_phi(), "region must have no phis");
1893
1894 return if_cont->as_Proj();
1895 }
1896
1897 //------------------------------find_predicate_insertion_point--------------------------
1898 // Find a good location to insert a predicate
1899 ProjNode* PhaseIdealLoop::find_predicate_insertion_point(Node* start_c) {
1900 if (start_c == C->root() || !start_c->is_Proj())
1901 return NULL;
1902 if (is_uncommon_trap_if_pattern(start_c->as_Proj(), true/*Reason_Predicate*/)) {
1903 return start_c->as_Proj();
1904 }
1905 return NULL;
1906 }
1907
1908 //------------------------------Invariance-----------------------------------
1909 // Helper class for loop_predication_impl to compute invariance on the fly and
1910 // clone invariants.
1911 class Invariance : public StackObj {
1912 VectorSet _visited, _invariant;
1913 Node_Stack _stack;
1914 VectorSet _clone_visited;
1915 Node_List _old_new; // map of old to new (clone)
1916 IdealLoopTree* _lpt;
1917 PhaseIdealLoop* _phase;
1918
1919 // Helper function to set up the invariance for invariance computation
1920 // If n is a known invariant, set up directly. Otherwise, look up the
1921 // the possibility to push n onto the stack for further processing.
1922 void visit(Node* use, Node* n) {
1923 if (_lpt->is_invariant(n)) { // known invariant
1924 _invariant.set(n->_idx);
1925 } else if (!n->is_CFG()) {
1926 Node *n_ctrl = _phase->ctrl_or_self(n);
1927 Node *u_ctrl = _phase->ctrl_or_self(use); // self if use is a CFG
1928 if (_phase->is_dominator(n_ctrl, u_ctrl)) {
1929 _stack.push(n, n->in(0) == NULL ? 1 : 0);
1930 }
1931 }
1932 }
1933
1934 // Compute invariance for "the_node" and (possibly) all its inputs recursively
1935 // on the fly
1936 void compute_invariance(Node* n) {
1937 assert(_visited.test(n->_idx), "must be");
1938 visit(n, n);
1939 while (_stack.is_nonempty()) {
1940 Node* n = _stack.node();
1941 uint idx = _stack.index();
1942 if (idx == n->req()) { // all inputs are processed
1943 _stack.pop();
1944 // n is invariant if it's inputs are all invariant
1945 bool all_inputs_invariant = true;
1946 for (uint i = 0; i < n->req(); i++) {
1947 Node* in = n->in(i);
1948 if (in == NULL) continue;
1949 assert(_visited.test(in->_idx), "must have visited input");
1950 if (!_invariant.test(in->_idx)) { // bad guy
1951 all_inputs_invariant = false;
1952 break;
1953 }
1954 }
1955 if (all_inputs_invariant) {
1956 _invariant.set(n->_idx); // I am a invariant too
1957 }
1958 } else { // process next input
1959 _stack.set_index(idx + 1);
1960 Node* m = n->in(idx);
1961 if (m != NULL && !_visited.test_set(m->_idx)) {
1962 visit(n, m);
1963 }
1964 }
1965 }
1966 }
1967
1968 // Helper function to set up _old_new map for clone_nodes.
1969 // If n is a known invariant, set up directly ("clone" of n == n).
1970 // Otherwise, push n onto the stack for real cloning.
1971 void clone_visit(Node* n) {
1972 assert(_invariant.test(n->_idx), "must be invariant");
1973 if (_lpt->is_invariant(n)) { // known invariant
1974 _old_new.map(n->_idx, n);
1975 } else{ // to be cloned
1976 assert (!n->is_CFG(), "should not see CFG here");
1977 _stack.push(n, n->in(0) == NULL ? 1 : 0);
1978 }
1979 }
1980
1981 // Clone "n" and (possibly) all its inputs recursively
1982 void clone_nodes(Node* n, Node* ctrl) {
1983 clone_visit(n);
1984 while (_stack.is_nonempty()) {
1985 Node* n = _stack.node();
1986 uint idx = _stack.index();
1987 if (idx == n->req()) { // all inputs processed, clone n!
1988 _stack.pop();
1989 // clone invariant node
1990 Node* n_cl = n->clone();
1991 _old_new.map(n->_idx, n_cl);
1992 _phase->register_new_node(n_cl, ctrl);
1993 for (uint i = 0; i < n->req(); i++) {
1994 Node* in = n_cl->in(i);
1995 if (in == NULL) continue;
1996 n_cl->set_req(i, _old_new[in->_idx]);
1997 }
1998 } else { // process next input
1999 _stack.set_index(idx + 1);
2000 Node* m = n->in(idx);
2001 if (m != NULL && !_clone_visited.test_set(m->_idx)) {
2002 clone_visit(m); // visit the input
2003 }
2004 }
2005 }
2006 }
2007
2008 public:
2009 Invariance(Arena* area, IdealLoopTree* lpt) :
2010 _lpt(lpt), _phase(lpt->_phase),
2011 _visited(area), _invariant(area), _stack(area, 10 /* guess */),
2012 _clone_visited(area), _old_new(area)
2013 {}
2014
2015 // Map old to n for invariance computation and clone
2016 void map_ctrl(Node* old, Node* n) {
2017 assert(old->is_CFG() && n->is_CFG(), "must be");
2018 _old_new.map(old->_idx, n); // "clone" of old is n
2019 _invariant.set(old->_idx); // old is invariant
2020 _clone_visited.set(old->_idx);
2021 }
2022
2023 // Driver function to compute invariance
2024 bool is_invariant(Node* n) {
2025 if (!_visited.test_set(n->_idx))
2026 compute_invariance(n);
2027 return (_invariant.test(n->_idx) != 0);
2028 }
2029
2030 // Driver function to clone invariant
2031 Node* clone(Node* n, Node* ctrl) {
2032 assert(ctrl->is_CFG(), "must be");
2033 assert(_invariant.test(n->_idx), "must be an invariant");
2034 if (!_clone_visited.test(n->_idx))
2035 clone_nodes(n, ctrl);
2036 return _old_new[n->_idx];
2037 }
2038 };
2039
2040 //------------------------------is_range_check_if -----------------------------------
2041 // Returns true if the predicate of iff is in "scale*iv + offset u< load_range(ptr)" format
2042 // Note: this function is particularly designed for loop predication. We require load_range
2043 // and offset to be loop invariant computed on the fly by "invar"
2044 bool IdealLoopTree::is_range_check_if(IfNode *iff, PhaseIdealLoop *phase, Invariance& invar) const {
2045 if (!is_loop_exit(iff)) {
2046 return false;
2047 }
2048 if (!iff->in(1)->is_Bool()) {
2049 return false;
2050 }
2051 const BoolNode *bol = iff->in(1)->as_Bool();
2052 if (bol->_test._test != BoolTest::lt) {
2053 return false;
2054 }
2055 if (!bol->in(1)->is_Cmp()) {
2056 return false;
2057 }
2058 const CmpNode *cmp = bol->in(1)->as_Cmp();
2059 if (cmp->Opcode() != Op_CmpU ) {
2060 return false;
2061 }
2062 Node* range = cmp->in(2);
2063 if (range->Opcode() != Op_LoadRange) {
2064 const TypeInt* tint = phase->_igvn.type(range)->isa_int();
2065 if (!OptimizeFill || tint == NULL || tint->empty() || tint->_lo < 0) {
2066 // Allow predication on positive values that aren't LoadRanges.
2067 // This allows optimization of loops where the length of the
2068 // array is a known value and doesn't need to be loaded back
2069 // from the array.
2070 return false;
2071 }
2072 }
2073 if (!invar.is_invariant(range)) {
2074 return false;
2075 }
2076 Node *iv = _head->as_CountedLoop()->phi();
2077 int scale = 0;
2078 Node *offset = NULL;
2079 if (!phase->is_scaled_iv_plus_offset(cmp->in(1), iv, &scale, &offset)) {
2080 return false;
2081 }
2082 if(offset && !invar.is_invariant(offset)) { // offset must be invariant
2083 return false;
2084 }
2085 return true;
2086 }
2087
2088 //------------------------------rc_predicate-----------------------------------
2089 // Create a range check predicate
2090 //
2091 // for (i = init; i < limit; i += stride) {
2092 // a[scale*i+offset]
2093 // }
2094 //
2095 // Compute max(scale*i + offset) for init <= i < limit and build the predicate
2096 // as "max(scale*i + offset) u< a.length".
2097 //
2098 // There are two cases for max(scale*i + offset):
2099 // (1) stride*scale > 0
2100 // max(scale*i + offset) = scale*(limit-stride) + offset
2101 // (2) stride*scale < 0
2102 // max(scale*i + offset) = scale*init + offset
2103 BoolNode* PhaseIdealLoop::rc_predicate(Node* ctrl,
2104 int scale, Node* offset,
2105 Node* init, Node* limit, Node* stride,
2106 Node* range, bool upper) {
2107 DEBUG_ONLY(ttyLocker ttyl);
2108 if (TraceLoopPredicate) tty->print("rc_predicate ");
2109
2110 Node* max_idx_expr = init;
2111 int stride_con = stride->get_int();
2112 if ((stride_con > 0) == (scale > 0) == upper) {
2113 max_idx_expr = new (C, 3) SubINode(limit, stride);
2114 register_new_node(max_idx_expr, ctrl);
2115 if (TraceLoopPredicate) tty->print("(limit - stride) ");
2116 } else {
2117 if (TraceLoopPredicate) tty->print("init ");
2118 }
2119
2120 if (scale != 1) {
2121 ConNode* con_scale = _igvn.intcon(scale);
2122 max_idx_expr = new (C, 3) MulINode(max_idx_expr, con_scale);
2123 register_new_node(max_idx_expr, ctrl);
2124 if (TraceLoopPredicate) tty->print("* %d ", scale);
2125 }
2126
2127 if (offset && (!offset->is_Con() || offset->get_int() != 0)){
2128 max_idx_expr = new (C, 3) AddINode(max_idx_expr, offset);
2129 register_new_node(max_idx_expr, ctrl);
2130 if (TraceLoopPredicate)
2131 if (offset->is_Con()) tty->print("+ %d ", offset->get_int());
2132 else tty->print("+ offset ");
2133 }
2134
2135 CmpUNode* cmp = new (C, 3) CmpUNode(max_idx_expr, range);
2136 register_new_node(cmp, ctrl);
2137 BoolNode* bol = new (C, 2) BoolNode(cmp, BoolTest::lt);
2138 register_new_node(bol, ctrl);
2139
2140 if (TraceLoopPredicate) tty->print_cr("<u range");
2141 return bol;
2142 }
2143
2144 //------------------------------ loop_predication_impl--------------------------
2145 // Insert loop predicates for null checks and range checks
2146 bool PhaseIdealLoop::loop_predication_impl(IdealLoopTree *loop) {
2147 if (!UseLoopPredicate) return false;
2148
2149 if (!loop->_head->is_Loop()) {
2150 // Could be a simple region when irreducible loops are present.
2151 return false;
2152 }
2153
2154 CountedLoopNode *cl = NULL;
2155 if (loop->_head->is_CountedLoop()) {
2156 cl = loop->_head->as_CountedLoop();
2157 // do nothing for iteration-splitted loops
2158 if (!cl->is_normal_loop()) return false;
2159 }
2160
2161 // Too many traps seen?
2162 bool tmt = C->too_many_traps(C->method(), 0, Deoptimization::Reason_predicate);
2163 int tc = C->trap_count(Deoptimization::Reason_predicate);
2164 if (tmt || tc > 0) {
2165 if (TraceLoopPredicate) {
2166 tty->print_cr("too many predicate traps: %d", tc);
2167 C->method()->print(); // which method has too many predicate traps
2168 tty->print_cr("");
2169 }
2170 return false;
2171 }
2172
2173 LoopNode *lpn = loop->_head->as_Loop();
2174 Node* entry = lpn->in(LoopNode::EntryControl);
2175
2176 ProjNode *predicate_proj = find_predicate_insertion_point(entry);
2177 if (!predicate_proj){
2178 #ifndef PRODUCT
2179 if (TraceLoopPredicate) {
2180 tty->print("missing predicate:");
2181 loop->dump_head();
2182 }
2183 #endif
2184 return false;
2185 }
2186
2187 ConNode* zero = _igvn.intcon(0);
2188 set_ctrl(zero, C->root());
2189 Node *cond_false = new (C, 2) Conv2BNode(zero);
2190 register_new_node(cond_false, C->root());
2191 ConNode* one = _igvn.intcon(1);
2192 set_ctrl(one, C->root());
2193 Node *cond_true = new (C, 2) Conv2BNode(one);
2194 register_new_node(cond_true, C->root());
2195
2196 ResourceArea *area = Thread::current()->resource_area();
2197 Invariance invar(area, loop);
2198
2199 // Create list of if-projs such that a newer proj dominates all older
2200 // projs in the list, and they all dominate loop->tail()
2201 Node_List if_proj_list(area);
2202 LoopNode *head = loop->_head->as_Loop();
2203 Node *current_proj = loop->tail(); //start from tail
2204 while ( current_proj != head ) {
2205 if (loop == get_loop(current_proj) && // still in the loop ?
2206 current_proj->is_Proj() && // is a projection ?
2207 current_proj->in(0)->Opcode() == Op_If) { // is a if projection ?
2208 if_proj_list.push(current_proj);
2209 }
2210 current_proj = idom(current_proj);
2211 }
2212
2213 bool hoisted = false; // true if at least one proj is promoted
2214 while (if_proj_list.size() > 0) {
2215 // Following are changed to nonnull when a predicate can be hoisted
2216 ProjNode* new_predicate_proj = NULL;
2217
2218 ProjNode* proj = if_proj_list.pop()->as_Proj();
2219 IfNode* iff = proj->in(0)->as_If();
2220
2221 if (!is_uncommon_trap_if_pattern(proj)) {
2222 if (loop->is_loop_exit(iff)) {
2223 // stop processing the remaining projs in the list because the execution of them
2224 // depends on the condition of "iff" (iff->in(1)).
2225 break;
2226 } else {
2227 // Both arms are inside the loop. There are two cases:
2228 // (1) there is one backward branch. In this case, any remaining proj
2229 // in the if_proj list post-dominates "iff". So, the condition of "iff"
2230 // does not determine the execution the remining projs directly, and we
2231 // can safely continue.
2232 // (2) both arms are forwarded, i.e. a diamond shape. In this case, "proj"
2233 // does not dominate loop->tail(), so it can not be in the if_proj list.
2234 continue;
2235 }
2236 }
2237
2238 Node* test = iff->in(1);
2239 if (!test->is_Bool()){ //Conv2B, ...
2240 continue;
2241 }
2242 BoolNode* bol = test->as_Bool();
2243 if (invar.is_invariant(bol)) {
2244 // Invariant test
2245 new_predicate_proj = create_new_if_for_predicate(predicate_proj);
2246 Node* ctrl = new_predicate_proj->in(0)->as_If()->in(0);
2247 BoolNode* new_predicate_bol = invar.clone(bol, ctrl)->as_Bool();
2248
2249 // Negate test if necessary
2250 bool negated = false;
2251 if (proj->_con != predicate_proj->_con) {
2252 new_predicate_bol = new (C, 2) BoolNode(new_predicate_bol->in(1), new_predicate_bol->_test.negate());
2253 register_new_node(new_predicate_bol, ctrl);
2254 negated = true;
2255 }
2256 IfNode* new_predicate_iff = new_predicate_proj->in(0)->as_If();
2257 _igvn.hash_delete(new_predicate_iff);
2258 new_predicate_iff->set_req(1, new_predicate_bol);
2259 if (TraceLoopPredicate) tty->print_cr("invariant if%s: %d", negated ? " negated" : "", new_predicate_iff->_idx);
2260
2261 } else if (cl != NULL && loop->is_range_check_if(iff, this, invar)) {
2262 assert(proj->_con == predicate_proj->_con, "must match");
2263
2264 // Range check for counted loops
2265 const Node* cmp = bol->in(1)->as_Cmp();
2266 Node* idx = cmp->in(1);
2267 assert(!invar.is_invariant(idx), "index is variant");
2268 assert(cmp->in(2)->Opcode() == Op_LoadRange || OptimizeFill, "must be");
2269 Node* rng = cmp->in(2);
2270 assert(invar.is_invariant(rng), "range must be invariant");
2271 int scale = 1;
2272 Node* offset = zero;
2273 bool ok = is_scaled_iv_plus_offset(idx, cl->phi(), &scale, &offset);
2274 assert(ok, "must be index expression");
2275
2276 Node* init = cl->init_trip();
2277 Node* limit = cl->limit();
2278 Node* stride = cl->stride();
2279
2280 // Build if's for the upper and lower bound tests. The
2281 // lower_bound test will dominate the upper bound test and all
2282 // cloned or created nodes will use the lower bound test as
2283 // their declared control.
2284 ProjNode* lower_bound_proj = create_new_if_for_predicate(predicate_proj);
2285 ProjNode* upper_bound_proj = create_new_if_for_predicate(predicate_proj);
2286 assert(upper_bound_proj->in(0)->as_If()->in(0) == lower_bound_proj, "should dominate");
2287 Node *ctrl = lower_bound_proj->in(0)->as_If()->in(0);
2288
2289 // Perform cloning to keep Invariance state correct since the
2290 // late schedule will place invariant things in the loop.
2291 rng = invar.clone(rng, ctrl);
2292 if (offset && offset != zero) {
2293 assert(invar.is_invariant(offset), "offset must be loop invariant");
2294 offset = invar.clone(offset, ctrl);
2295 }
2296
2297 // Test the lower bound
2298 Node* lower_bound_bol = rc_predicate(ctrl, scale, offset, init, limit, stride, rng, false);
2299 IfNode* lower_bound_iff = lower_bound_proj->in(0)->as_If();
2300 _igvn.hash_delete(lower_bound_iff);
2301 lower_bound_iff->set_req(1, lower_bound_bol);
2302 if (TraceLoopPredicate) tty->print_cr("lower bound check if: %d", lower_bound_iff->_idx);
2303
2304 // Test the upper bound
2305 Node* upper_bound_bol = rc_predicate(ctrl, scale, offset, init, limit, stride, rng, true);
2306 IfNode* upper_bound_iff = upper_bound_proj->in(0)->as_If();
2307 _igvn.hash_delete(upper_bound_iff);
2308 upper_bound_iff->set_req(1, upper_bound_bol);
2309 if (TraceLoopPredicate) tty->print_cr("upper bound check if: %d", lower_bound_iff->_idx);
2310
2311 // Fall through into rest of the clean up code which will move
2312 // any dependent nodes onto the upper bound test.
2313 new_predicate_proj = upper_bound_proj;
2314 } else {
2315 // The other proj of the "iff" is a uncommon trap projection, and we can assume
2316 // the other proj will not be executed ("executed" means uct raised).
2317 continue;
2318 }
2319
2320 // Success - attach condition (new_predicate_bol) to predicate if
2321 invar.map_ctrl(proj, new_predicate_proj); // so that invariance test can be appropriate
2322
2323 // Eliminate the old if in the loop body
2324 _igvn.hash_delete(iff);
2325 iff->set_req(1, proj->is_IfFalse() ? cond_false : cond_true);
2326
2327 Node* ctrl = new_predicate_proj; // new control
2328 ProjNode* dp = proj; // old control
2329 assert(get_loop(dp) == loop, "guaranteed at the time of collecting proj");
2330 // Find nodes (depends only on the test) off the surviving projection;
2331 // move them outside the loop with the control of proj_clone
2332 for (DUIterator_Fast imax, i = dp->fast_outs(imax); i < imax; i++) {
2333 Node* cd = dp->fast_out(i); // Control-dependent node
2334 if (cd->depends_only_on_test()) {
2335 assert(cd->in(0) == dp, "");
2336 _igvn.hash_delete(cd);
2337 cd->set_req(0, ctrl); // ctrl, not NULL
2338 set_early_ctrl(cd);
2339 _igvn._worklist.push(cd);
2340 IdealLoopTree *new_loop = get_loop(get_ctrl(cd));
2341 if (new_loop != loop) {
2342 if (!loop->_child) loop->_body.yank(cd);
2343 if (!new_loop->_child ) new_loop->_body.push(cd);
2344 }
2345 --i;
2346 --imax;
2347 }
2348 }
2349
2350 hoisted = true;
2351 C->set_major_progress();
2352 } // end while
2353
2354 #ifndef PRODUCT
2355 // report that the loop predication has been actually performed
2356 // for this loop
2357 if (TraceLoopPredicate && hoisted) {
2358 tty->print("Loop Predication Performed:");
2359 loop->dump_head();
2360 }
2361 #endif
2362
2363 return hoisted;
2364 }
2365
2366 //------------------------------loop_predication--------------------------------
2367 // driver routine for loop predication optimization
2368 bool IdealLoopTree::loop_predication( PhaseIdealLoop *phase) {
2369 bool hoisted = false;
2370 // Recursively promote predicates
2371 if ( _child ) {
2372 hoisted = _child->loop_predication( phase);
2373 }
2374
2375 // self
2376 if (!_irreducible && !tail()->is_top()) {
2377 hoisted |= phase->loop_predication_impl(this);
2378 }
2379
2380 if ( _next ) { //sibling
2381 hoisted |= _next->loop_predication( phase);
2382 }
2383
2384 return hoisted;
2385 }
2386
2387
2388 // Process all the loops in the loop tree and replace any fill
2389 // patterns with an intrisc version.
2390 bool PhaseIdealLoop::do_intrinsify_fill() {
2391 bool changed = false;
2392 for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
2393 IdealLoopTree* lpt = iter.current();
2394 changed |= intrinsify_fill(lpt);
2395 }
2396 return changed;
2397 }
2398
2399
2400 // Examine an inner loop looking for a a single store of an invariant
2401 // value in a unit stride loop,
2402 bool PhaseIdealLoop::match_fill_loop(IdealLoopTree* lpt, Node*& store, Node*& store_value,
2403 Node*& shift, Node*& con) {
2404 const char* msg = NULL;
2405 Node* msg_node = NULL;
2406
2407 store_value = NULL;
2408 con = NULL;
2409 shift = NULL;
2410
2411 // Process the loop looking for stores. If there are multiple
2412 // stores or extra control flow give at this point.
2413 CountedLoopNode* head = lpt->_head->as_CountedLoop();
2414 for (uint i = 0; msg == NULL && i < lpt->_body.size(); i++) {
2415 Node* n = lpt->_body.at(i);
2416 if (n->outcnt() == 0) continue; // Ignore dead
2417 if (n->is_Store()) {
2418 if (store != NULL) {
2419 msg = "multiple stores";
2420 break;
2421 }
2422 int opc = n->Opcode();
2423 if (opc == Op_StoreP || opc == Op_StoreN || opc == Op_StoreCM) {
2424 msg = "oop fills not handled";
2425 break;
2426 }
2427 Node* value = n->in(MemNode::ValueIn);
2428 if (!lpt->is_invariant(value)) {
2429 msg = "variant store value";
2430 } else if (!_igvn.type(n->in(MemNode::Address))->isa_aryptr()) {
2431 msg = "not array address";
2432 }
2433 store = n;
2434 store_value = value;
2435 } else if (n->is_If() && n != head->loopexit()) {
2436 msg = "extra control flow";
2437 msg_node = n;
2438 }
2439 }
2440
2441 if (store == NULL) {
2442 // No store in loop
2443 return false;
2444 }
2445
2446 if (msg == NULL && head->stride_con() != 1) {
2447 // could handle negative strides too
2448 if (head->stride_con() < 0) {
2449 msg = "negative stride";
2450 } else {
2451 msg = "non-unit stride";
2452 }
2453 }
2454
2455 if (msg == NULL && !store->in(MemNode::Address)->is_AddP()) {
2456 msg = "can't handle store address";
2457 msg_node = store->in(MemNode::Address);
2458 }
2459
2460 if (msg == NULL &&
2461 (!store->in(MemNode::Memory)->is_Phi() ||
2462 store->in(MemNode::Memory)->in(LoopNode::LoopBackControl) != store)) {
2463 msg = "store memory isn't proper phi";
2464 msg_node = store->in(MemNode::Memory);
2465 }
2466
2467 // Make sure there is an appropriate fill routine
2468 BasicType t = store->as_Mem()->memory_type();
2469 const char* fill_name;
2470 if (msg == NULL &&
2471 StubRoutines::select_fill_function(t, false, fill_name) == NULL) {
2472 msg = "unsupported store";
2473 msg_node = store;
2474 }
2475
2476 if (msg != NULL) {
2477 #ifndef PRODUCT
2478 if (TraceOptimizeFill) {
2479 tty->print_cr("not fill intrinsic candidate: %s", msg);
2480 if (msg_node != NULL) msg_node->dump();
2481 }
2482 #endif
2483 return false;
2484 }
2485
2486 // Make sure the address expression can be handled. It should be
2487 // head->phi * elsize + con. head->phi might have a ConvI2L.
2488 Node* elements[4];
2489 Node* conv = NULL;
2490 bool found_index = false;
2491 int count = store->in(MemNode::Address)->as_AddP()->unpack_offsets(elements, ARRAY_SIZE(elements));
2492 for (int e = 0; e < count; e++) {
2493 Node* n = elements[e];
2494 if (n->is_Con() && con == NULL) {
2495 con = n;
2496 } else if (n->Opcode() == Op_LShiftX && shift == NULL) {
2497 Node* value = n->in(1);
2498 #ifdef _LP64
2499 if (value->Opcode() == Op_ConvI2L) {
2500 conv = value;
2501 value = value->in(1);
2502 }
2503 #endif
2504 if (value != head->phi()) {
2505 msg = "unhandled shift in address";
2506 } else {
2507 found_index = true;
2508 shift = n;
2509 assert(type2aelembytes(store->as_Mem()->memory_type(), true) == 1 << shift->in(2)->get_int(), "scale should match");
2510 }
2511 } else if (n->Opcode() == Op_ConvI2L && conv == NULL) {
2512 if (n->in(1) == head->phi()) {
2513 found_index = true;
2514 conv = n;
2515 } else {
2516 msg = "unhandled input to ConvI2L";
2517 }
2518 } else if (n == head->phi()) {
2519 // no shift, check below for allowed cases
2520 found_index = true;
2521 } else {
2522 msg = "unhandled node in address";
2523 msg_node = n;
2524 }
2525 }
2526
2527 if (count == -1) {
2528 msg = "malformed address expression";
2529 msg_node = store;
2530 }
2531
2532 if (!found_index) {
2533 msg = "missing use of index";
2534 }
2535
2536 // byte sized items won't have a shift
2537 if (msg == NULL && shift == NULL && t != T_BYTE && t != T_BOOLEAN) {
2538 msg = "can't find shift";
2539 msg_node = store;
2540 }
2541
2542 if (msg != NULL) {
2543 #ifndef PRODUCT
2544 if (TraceOptimizeFill) {
2545 tty->print_cr("not fill intrinsic: %s", msg);
2546 if (msg_node != NULL) msg_node->dump();
2547 }
2548 #endif
2549 return false;
2550 }
2551
2552 // No make sure all the other nodes in the loop can be handled
2553 VectorSet ok(Thread::current()->resource_area());
2554
2555 // store related values are ok
2556 ok.set(store->_idx);
2557 ok.set(store->in(MemNode::Memory)->_idx);
2558
2559 // Loop structure is ok
2560 ok.set(head->_idx);
2561 ok.set(head->loopexit()->_idx);
2562 ok.set(head->phi()->_idx);
2563 ok.set(head->incr()->_idx);
2564 ok.set(head->loopexit()->cmp_node()->_idx);
2565 ok.set(head->loopexit()->in(1)->_idx);
2566
2567 // Address elements are ok
2568 if (con) ok.set(con->_idx);
2569 if (shift) ok.set(shift->_idx);
2570 if (conv) ok.set(conv->_idx);
2571
2572 for (uint i = 0; msg == NULL && i < lpt->_body.size(); i++) {
2573 Node* n = lpt->_body.at(i);
2574 if (n->outcnt() == 0) continue; // Ignore dead
2575 if (ok.test(n->_idx)) continue;
2576 // Backedge projection is ok
2577 if (n->is_IfTrue() && n->in(0) == head->loopexit()) continue;
2578 if (!n->is_AddP()) {
2579 msg = "unhandled node";
2580 msg_node = n;
2581 break;
2582 }
2583 }
2584
2585 // Make sure no unexpected values are used outside the loop
2586 for (uint i = 0; msg == NULL && i < lpt->_body.size(); i++) {
2587 Node* n = lpt->_body.at(i);
2588 // These values can be replaced with other nodes if they are used
2589 // outside the loop.
2590 if (n == store || n == head->loopexit() || n == head->incr() || n == store->in(MemNode::Memory)) continue;
2591 for (SimpleDUIterator iter(n); iter.has_next(); iter.next()) {
2592 Node* use = iter.get();
2593 if (!lpt->_body.contains(use)) {
2594 msg = "node is used outside loop";
2595 // lpt->_body.dump();
2596 msg_node = n;
2597 break;
2598 }
2599 }
2600 }
2601
2602 #ifdef ASSERT
2603 if (TraceOptimizeFill) {
2604 if (msg != NULL) {
2605 tty->print_cr("no fill intrinsic: %s", msg);
2606 if (msg_node != NULL) msg_node->dump();
2607 } else {
2608 tty->print_cr("fill intrinsic for:");
2609 }
2610 store->dump();
2611 if (Verbose) {
2612 lpt->_body.dump();
2613 }
2614 }
2615 #endif
2616
2617 return msg == NULL;
2618 }
2619
2620
2621
2622 bool PhaseIdealLoop::intrinsify_fill(IdealLoopTree* lpt) {
2623 // Only for counted inner loops
2624 if (!lpt->is_counted() || !lpt->is_inner()) {
2625 return false;
2626 }
2627
2628 // Must have constant stride
2629 CountedLoopNode* head = lpt->_head->as_CountedLoop();
2630 if (!head->stride_is_con() || !head->is_normal_loop()) {
2631 return false;
2632 }
2633
2634 // Check that the body only contains a store of a loop invariant
2635 // value that is indexed by the loop phi.
2636 Node* store = NULL;
2637 Node* store_value = NULL;
2638 Node* shift = NULL;
2639 Node* offset = NULL;
2640 if (!match_fill_loop(lpt, store, store_value, shift, offset)) {
2641 return false;
2642 }
2643
2644 // Now replace the whole loop body by a call to a fill routine that
2645 // covers the same region as the loop.
2646 Node* base = store->in(MemNode::Address)->as_AddP()->in(AddPNode::Base);
2647
2648 // Build an expression for the beginning of the copy region
2649 Node* index = head->init_trip();
2650 #ifdef _LP64
2651 index = new (C, 2) ConvI2LNode(index);
2652 _igvn.register_new_node_with_optimizer(index);
2653 #endif
2654 if (shift != NULL) {
2655 // byte arrays don't require a shift but others do.
2656 index = new (C, 3) LShiftXNode(index, shift->in(2));
2657 _igvn.register_new_node_with_optimizer(index);
2658 }
2659 index = new (C, 4) AddPNode(base, base, index);
2660 _igvn.register_new_node_with_optimizer(index);
2661 Node* from = new (C, 4) AddPNode(base, index, offset);
2662 _igvn.register_new_node_with_optimizer(from);
2663 // Compute the number of elements to copy
2664 Node* len = new (C, 3) SubINode(head->limit(), head->init_trip());
2665 _igvn.register_new_node_with_optimizer(len);
2666
2667 BasicType t = store->as_Mem()->memory_type();
2668 bool aligned = false;
2669 if (offset != NULL && head->init_trip()->is_Con()) {
2670 int element_size = type2aelembytes(t);
2671 aligned = (offset->find_intptr_t_type()->get_con() + head->init_trip()->get_int() * element_size) % HeapWordSize == 0;
2672 }
2673
2674 // Build a call to the fill routine
2675 const char* fill_name;
2676 address fill = StubRoutines::select_fill_function(t, aligned, fill_name);
2677 assert(fill != NULL, "what?");
2678
2679 // Convert float/double to int/long for fill routines
2680 if (t == T_FLOAT) {
2681 store_value = new (C, 2) MoveF2INode(store_value);
2682 _igvn.register_new_node_with_optimizer(store_value);
2683 } else if (t == T_DOUBLE) {
2684 store_value = new (C, 2) MoveD2LNode(store_value);
2685 _igvn.register_new_node_with_optimizer(store_value);
2686 }
2687
2688 Node* mem_phi = store->in(MemNode::Memory);
2689 Node* result_ctrl;
2690 Node* result_mem;
2691 const TypeFunc* call_type = OptoRuntime::array_fill_Type();
2692 int size = call_type->domain()->cnt();
2693 CallLeafNode *call = new (C, size) CallLeafNoFPNode(call_type, fill,
2694 fill_name, TypeAryPtr::get_array_body_type(t));
2695 call->init_req(TypeFunc::Parms+0, from);
2696 call->init_req(TypeFunc::Parms+1, store_value);
2697 #ifdef _LP64
2698 len = new (C, 2) ConvI2LNode(len);
2699 _igvn.register_new_node_with_optimizer(len);
2700 #endif
2701 call->init_req(TypeFunc::Parms+2, len);
2702 #ifdef _LP64
2703 call->init_req(TypeFunc::Parms+3, C->top());
2704 #endif
2705 call->init_req( TypeFunc::Control, head->init_control());
2706 call->init_req( TypeFunc::I_O , C->top() ) ; // does no i/o
2707 call->init_req( TypeFunc::Memory , mem_phi->in(LoopNode::EntryControl) );
2708 call->init_req( TypeFunc::ReturnAdr, C->start()->proj_out(TypeFunc::ReturnAdr) );
2709 call->init_req( TypeFunc::FramePtr, C->start()->proj_out(TypeFunc::FramePtr) );
2710 _igvn.register_new_node_with_optimizer(call);
2711 result_ctrl = new (C, 1) ProjNode(call,TypeFunc::Control);
2712 _igvn.register_new_node_with_optimizer(result_ctrl);
2713 result_mem = new (C, 1) ProjNode(call,TypeFunc::Memory);
2714 _igvn.register_new_node_with_optimizer(result_mem);
2715
2716 // If this fill is tightly coupled to an allocation and overwrites
2717 // the whole body, allow it to take over the zeroing.
2718 AllocateNode* alloc = AllocateNode::Ideal_allocation(base, this);
2719 if (alloc != NULL && alloc->is_AllocateArray()) {
2720 Node* length = alloc->as_AllocateArray()->Ideal_length();
2721 if (head->limit() == length &&
2722 head->init_trip() == _igvn.intcon(0)) {
2723 if (TraceOptimizeFill) {
2724 tty->print_cr("Eliminated zeroing in allocation");
2725 }
2726 alloc->maybe_set_complete(&_igvn);
2727 } else {
2728 #ifdef ASSERT
2729 if (TraceOptimizeFill) {
2730 tty->print_cr("filling array but bounds don't match");
2731 alloc->dump();
2732 head->init_trip()->dump();
2733 head->limit()->dump();
2734 length->dump();
2735 }
2736 #endif
2737 }
2738 }
2739
2740 // Redirect the old control and memory edges that are outside the loop.
2741 Node* exit = head->loopexit()->proj_out(0);
2742 // Sometimes the memory phi of the head is used as the outgoing
2743 // state of the loop. It's safe in this case to replace it with the
2744 // result_mem.
2745 _igvn.replace_node(store->in(MemNode::Memory), result_mem);
2746 _igvn.replace_node(exit, result_ctrl);
2747 _igvn.replace_node(store, result_mem);
2748 // Any uses the increment outside of the loop become the loop limit.
2749 _igvn.replace_node(head->incr(), head->limit());
2750
2751 // Disconnect the head from the loop.
2752 for (uint i = 0; i < lpt->_body.size(); i++) {
2753 Node* n = lpt->_body.at(i);
2754 _igvn.replace_node(n, C->top());
2755 }
2756
2757 return true;
2758 }